Sonotube Size Guide: How Many Bags of Concrete Per Tube?
| Diameter | 2 ft deep | 3 ft deep | 4 ft deep |
|---|---|---|---|
| 6 inch | 1 bag | 2 bags | 2 bags |
| 8 inch | 2 bags | 2 bags | 3 bags |
| 10 inch | 2 bags | 3 bags | 4 bags |
| 12 inch | 3 bags | 5 bags | 6 bags |
| 14 inch | 4 bags | 6 bags | 8 bags |
| 16 inch | 6 bags | 8 bags | 11 bags |
| 18 inch | 7 bags | 10 bags | 13 bags |
| 24 inch | 12 bags | 18 bags | 24 bags |
All counts include 10% overage and assume standard 80 lb bags that yield about 0.60 ft3 each. The most common residential deck pier, a 12-inch tube at 4 feet deep, needs 6 bags.
-> Use the free calculator below for exact counts and multiple-pier totals.
Sonotubes are the round cardboard tube forms used for deck piers, fence posts, pergola footings, and column bases. They are simple to shop for but easy to underestimate. The amount of concrete inside a tube depends on two variables only: diameter and depth. Because cylinder volume grows with the square of the radius, even a modest jump in diameter can add several more bags per pier.
This guide gives you the complete Sonotube size overview, live bag-count tables for the standard diameters from 6 to 24 inches, a free tube calculator, and a practical decision guide for sizing deck and post footings. It also covers frost depth, brand comparisons, and the step-by-step installation sequence so you can plan the full project instead of just the shopping list.
In This Article
- 1. Quick Reference Table
- 2. Sonotube Sizes at a Glance
- 3. Free Sonotube Concrete Calculator
- 4. Full Bag Count Matrix
- 5. Bag Counts by Diameter
- 6. What Size Sonotube Do I Need?
- 7. How Deep Should a Sonotube Be?
- 8. Sonotube vs. Quik-Tube vs. Generic Tube Forms
- 9. How to Set a Sonotube and Pour Concrete
- 10. Common Mistakes
- 11. FAQ
Sonotube Sizes at a Glance
Standard tube-form shopping usually starts with diameter, not concrete volume, so it helps to know how the sizes stack up before you price the bags. The table below shows the standard diameters people actually buy, the concrete volume each diameter holds per foot of depth, and the kind of work each size is usually paired with.
Sonotube sizes at a glance
| Diameter | Volume / foot (ft3) | Volume / foot (yd3) | Bearing at 4,000 psf* | Common use |
|---|---|---|---|---|
| 6 inch | 0.196 ft3 | 0.0073 yd3 | ~775 lb | Mailbox and light fence posts |
| 8 inch | 0.349 ft3 | 0.0129 yd3 | ~1,400 lb | Fence posts and light pergolas |
| 10 inch | 0.545 ft3 | 0.0202 yd3 | ~2,200 lb | Light deck piers and sheds |
| 12 inch | 0.785 ft3 | 0.0291 yd3 | ~3,150 lb | Standard residential deck piers |
| 14 inch | 1.069 ft3 | 0.0396 yd3 | ~4,300 lb | Heavy decks and pergolas |
| 16 inch | 1.396 ft3 | 0.0517 yd3 | ~5,600 lb | Carports and heavier structures |
| 18 inch | 1.767 ft3 | 0.0654 yd3 | ~7,050 lb | Large timber posts and pavilions |
| 24 inch | 3.142 ft3 | 0.1164 yd3 | ~12,550 lb | Large columns and commercial work |
*Approximate centered soil-bearing load using 4,000 psf allowable soil pressure only. Real footing design also depends on local code, uplift, eccentric loading, reinforcement, and frost requirements. Use the labeled tube diameter, which refers to the inside diameter.
The 12-inch Sonotube is the center of gravity for residential deck construction. It is large enough to be the default in many permit offices, but still small enough that the bag count remains manageable for DIY pours. That balance is why 12-inch by 4-foot piers show up repeatedly in deck plans and search queries.
If you are still deciding whether to buy bagged concrete at all, compare these tube volumes with the broader bag count guide and the concrete cost per yard guide. Larger diameters can cross into ready-mix territory quickly.
Free Sonotube Concrete Calculator
Select the tube diameter, enter the depth, and multiply by the number of piers to see the full bag count instantly. This article version keeps the workflow intentionally compact for fast planning on mobile or while comparing deck pier layouts.
Tip: multiply the per-tube bag count by the number of piers in your layout before you shop. If you need custom diameters or a printable estimate, open the full Tube Calculator.
How Many Bags of Concrete Per Sonotube?
The matrix tables below cover the standard diameters from 6 to 24 inches and common depths from 2 to 8 feet. They are generated from the same cylinder-volume formula used by the calculator, so the FAQ answers, quick-reference card, and the detailed diameter sections all stay aligned.
80 lb Bag Count Matrix
| Diameter | 2 ft | 3 ft | 4 ft | 5 ft | 6 ft | 7 ft | 8 ft |
|---|---|---|---|---|---|---|---|
| 6 in | 1 | 2 | 2 | 2 | 3 | 3 | 3 |
| 8 in | 2 | 2 | 3 | 4 | 4 | 5 | 6 |
| 10 in | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| 12 in | 3 | 5 | 6 | 8 | 9 | 11 | 12 |
| 14 in | 4 | 6 | 8 | 10 | 12 | 14 | 16 |
| 16 in | 6 | 8 | 11 | 13 | 16 | 18 | 21 |
| 18 in | 7 | 10 | 13 | 17 | 20 | 23 | 26 |
| 24 in | 12 | 18 | 24 | 29 | 35 | 41 | 47 |
Counts are formula-based using 0.60 ft3 yield per 80 lb bag, a 10% overage allowance, and a full cylindrical fill. Round up; do not round down when buying bagged concrete.
60 lb Bag Count Matrix
| Diameter | 2 ft | 3 ft | 4 ft | 5 ft | 6 ft | 7 ft | 8 ft |
|---|---|---|---|---|---|---|---|
| 6 in | 1 | 2 | 2 | 3 | 3 | 4 | 4 |
| 8 in | 2 | 3 | 4 | 5 | 6 | 6 | 7 |
| 10 in | 3 | 4 | 6 | 7 | 8 | 10 | 11 |
| 12 in | 4 | 6 | 8 | 10 | 12 | 14 | 16 |
| 14 in | 6 | 8 | 11 | 14 | 16 | 19 | 21 |
| 16 in | 7 | 11 | 14 | 18 | 21 | 24 | 28 |
| 18 in | 9 | 13 | 18 | 22 | 26 | 31 | 35 |
| 24 in | 16 | 24 | 31 | 39 | 47 | 54 | 62 |
Counts are formula-based using 0.45 ft3 yield per 60 lb bag and the same 10% overage. This is the easier-to-handle option for solo DIY pours.
40 lb Bag Count Matrix
| Diameter | 2 ft | 3 ft | 4 ft | 5 ft | 6 ft | 7 ft | 8 ft |
|---|---|---|---|---|---|---|---|
| 6 in | 2 | 3 | 3 | 4 | 5 | 6 | 6 |
| 8 in | 3 | 4 | 6 | 7 | 8 | 9 | 11 |
| 10 in | 4 | 6 | 8 | 10 | 12 | 14 | 16 |
| 12 in | 6 | 9 | 12 | 15 | 18 | 21 | 24 |
| 14 in | 8 | 12 | 16 | 20 | 24 | 28 | 32 |
| 16 in | 11 | 16 | 21 | 26 | 31 | 36 | 41 |
| 18 in | 13 | 20 | 26 | 33 | 39 | 46 | 52 |
| 24 in | 24 | 35 | 47 | 58 | 70 | 81 | 93 |
Counts are formula-based using 0.30 ft3 yield per 40 lb bag and the same 10% overage. Use this table only when lighter bags are the priority.
For most deck-pier work, 80 lb bags are still the most efficient option because they offer the best yield per bag. If you are working alone, 60 lb bags reduce the lift weight at the cost of more trips between the mixer and the tube. Forty-pound bags are workable, but mainly when weight handling matters more than speed.
If your shopping list starts to look excessive, switch to the full Bag Calculator to compare bag sizes more broadly, or jump to the ready-mix price guide to check whether truck delivery is the smarter path.
Bag Counts by Sonotube Diameter
Bag counts become easier to trust when you can see them attached to a specific diameter and a realistic use case. The breakdown below covers each standard Sonotube size individually so you can match your project to the right size instead of reading a single generic table in isolation.
6-Inch Sonotube - Bag Count and Specifications
The 6-inch Sonotube is the smallest common tube form and belongs on light-duty work only: mailbox posts, small fence posts, and landscape anchors. It is compact, economical, and easy to fill with bagged concrete, but it does not offer enough bearing area for typical residential deck loads.
If you only need a small pier that keeps a wood post isolated from soil and splashback, this size is efficient. The moment the load becomes structural, especially for decks, pergolas, or sheds, move up at least one or two diameters.
6-inch Sonotube bag counts
| Depth | Volume (yd3) | With Overage | 40 lb | 60 lb | 80 lb |
|---|---|---|---|---|---|
| 2 ft | 0.015 yd3 | 0.016 yd3 | 2 | 1 | 1 |
| 3 ft | 0.022 yd3 | 0.024 yd3 | 3 | 2 | 2 |
| 4 ft | 0.029 yd3 | 0.032 yd3 | 3 | 2 | 2 |
| 5 ft | 0.036 yd3 | 0.04 yd3 | 4 | 3 | 2 |
| 6 ft | 0.044 yd3 | 0.048 yd3 | 5 | 3 | 3 |
Volume is net cylindrical fill. Bag counts round up to whole bags and already include 10% overage, which is the safer field-buying number.
8-Inch Sonotube - Bag Count and Specifications
An 8-inch tube is a practical upgrade for fence posts, gate posts, and light pergola corners where you want more bearing area and better resistance against movement. It is still a small bagged-concrete job for most 2 to 4 foot depths.
For deck work, 8-inch forms are usually too small unless the application is very light and approved locally. Most homeowners looking for deck pier guidance should treat 10 inches as the low end and 12 inches as the safer default.
8-inch Sonotube bag counts
| Depth | Volume (yd3) | With Overage | 40 lb | 60 lb | 80 lb |
|---|---|---|---|---|---|
| 2 ft | 0.026 yd3 | 0.028 yd3 | 3 | 2 | 2 |
| 3 ft | 0.039 yd3 | 0.043 yd3 | 4 | 3 | 2 |
| 4 ft | 0.052 yd3 | 0.057 yd3 | 6 | 4 | 3 |
| 5 ft | 0.065 yd3 | 0.071 yd3 | 7 | 5 | 4 |
| 6 ft | 0.078 yd3 | 0.085 yd3 | 8 | 6 | 4 |
Volume is net cylindrical fill. Bag counts round up to whole bags and already include 10% overage, which is the safer field-buying number.
10-Inch Sonotube - Bag Count and Specifications
A 10-inch Sonotube is often the first diameter that enters deck-pier territory. It can work for light residential decks, small sheds, and moderate pergola loads when tributary area per pier stays limited and the soil is decent.
Bag count rises faster than many DIYers expect at this point. A 10-inch tube 4 feet deep already needs 4 bags of 80 lb mix with overage, so a six-pier layout means roughly 24 bags before you buy any gravel, hardware, or reinforcement.
10-inch Sonotube bag counts
| Depth | Volume (yd3) | With Overage | 40 lb | 60 lb | 80 lb |
|---|---|---|---|---|---|
| 2 ft | 0.04 yd3 | 0.044 yd3 | 4 | 3 | 2 |
| 3 ft | 0.061 yd3 | 0.067 yd3 | 6 | 4 | 3 |
| 4 ft | 0.081 yd3 | 0.089 yd3 | 8 | 6 | 4 |
| 5 ft | 0.101 yd3 | 0.111 yd3 | 10 | 7 | 5 |
| 6 ft | 0.121 yd3 | 0.133 yd3 | 12 | 8 | 6 |
Volume is net cylindrical fill. Bag counts round up to whole bags and already include 10% overage, which is the safer field-buying number.
12-Inch Sonotube - Bag Count and Specifications
The 12-inch Sonotube is the standard residential deck pier size in most markets. It balances meaningful bearing area, code-friendly sizing, and bag counts that are still manageable for DIY work. That is why search volume clusters around one question: how many bags do I need for a 12-inch tube?
For the most common deck-pier configuration, 12 inches in diameter and 4 feet deep, the answer is 6 bags of 80 lb concrete mix per pier with 10% overage included. A six-pier deck therefore lands at roughly 36 bags, while an eight-pier layout lands around 48 bags.
12-inch Sonotube bag counts
| Depth | Volume (yd3) | With Overage | 40 lb | 60 lb | 80 lb |
|---|---|---|---|---|---|
| 2 ft | 0.058 yd3 | 0.064 yd3 | 6 | 4 | 3 |
| 3 ft | 0.087 yd3 | 0.096 yd3 | 9 | 6 | 5 |
| 4 ft | 0.116 yd3 | 0.128 yd3 | 12 | 8 | 6 |
| 5 ft | 0.145 yd3 | 0.16 yd3 | 15 | 10 | 8 |
| 6 ft | 0.175 yd3 | 0.192 yd3 | 18 | 12 | 9 |
| 7 ft | 0.204 yd3 | 0.224 yd3 | 21 | 14 | 11 |
| 8 ft | 0.233 yd3 | 0.256 yd3 | 24 | 16 | 12 |
Volume is net cylindrical fill. Bag counts round up to whole bags and already include 10% overage, which is the safer field-buying number.
14-Inch Sonotube - Bag Count and Specifications
A 14-inch tube is a good move when loads or spans increase. It shows up under heavy decks, pergolas with wider beam spacing, outdoor kitchens, and projects where soil conditions are mediocre and extra bearing area buys useful margin.
The jump from 12 inches to 14 inches is not small. Tube volume grows with the square of the radius, so every diameter increase adds more concrete than most shoppers expect. Price the larger size deliberately instead of assuming it is just one extra bag.
14-inch Sonotube bag counts
| Depth | Volume (yd3) | With Overage | 40 lb | 60 lb | 80 lb |
|---|---|---|---|---|---|
| 2 ft | 0.079 yd3 | 0.087 yd3 | 8 | 6 | 4 |
| 3 ft | 0.119 yd3 | 0.131 yd3 | 12 | 8 | 6 |
| 4 ft | 0.158 yd3 | 0.174 yd3 | 16 | 11 | 8 |
| 5 ft | 0.198 yd3 | 0.218 yd3 | 20 | 14 | 10 |
| 6 ft | 0.238 yd3 | 0.261 yd3 | 24 | 16 | 12 |
Volume is net cylindrical fill. Bag counts round up to whole bags and already include 10% overage, which is the safer field-buying number.
16-Inch Sonotube - Bag Count and Specifications
A 16-inch form is common for heavier pergolas, pavilions, carports, and light commercial-looking residential work where uplift, eccentric loading, or wide tributary areas start to matter. At this size, planning the bag count before shopping is important because the labor burden ramps quickly.
A single 16-inch pier at 4 feet deep needs 11 bags of 80 lb mix with overage. If you have several piers at this size, compare the total bag weight and mixing time against ready-mix, especially if the site is accessible.
16-inch Sonotube bag counts
| Depth | Volume (yd3) | With Overage | 40 lb | 60 lb | 80 lb |
|---|---|---|---|---|---|
| 2 ft | 0.103 yd3 | 0.114 yd3 | 11 | 7 | 6 |
| 3 ft | 0.155 yd3 | 0.171 yd3 | 16 | 11 | 8 |
| 4 ft | 0.207 yd3 | 0.228 yd3 | 21 | 14 | 11 |
| 5 ft | 0.259 yd3 | 0.284 yd3 | 26 | 18 | 13 |
| 6 ft | 0.31 yd3 | 0.341 yd3 | 31 | 21 | 16 |
Volume is net cylindrical fill. Bag counts round up to whole bags and already include 10% overage, which is the safer field-buying number.
18-Inch Sonotube - Bag Count and Specifications
An 18-inch Sonotube moves into heavy-duty residential and light commercial territory. Pavilion posts, large timber frames, and engineered deck supports are common examples, but this is the point where local structural review matters much more than rules of thumb.
The practical takeaway is simple: bagged concrete is still possible at this size, but it stops being convenient. A small group of piers can consume dozens of bags quickly, so material handling becomes part of the cost and schedule decision.
18-inch Sonotube bag counts
| Depth | Volume (yd3) | With Overage | 40 lb | 60 lb | 80 lb |
|---|---|---|---|---|---|
| 2 ft | 0.131 yd3 | 0.144 yd3 | 13 | 9 | 7 |
| 3 ft | 0.196 yd3 | 0.216 yd3 | 20 | 13 | 10 |
| 4 ft | 0.262 yd3 | 0.288 yd3 | 26 | 18 | 13 |
| 5 ft | 0.327 yd3 | 0.36 yd3 | 33 | 22 | 17 |
| 6 ft | 0.393 yd3 | 0.432 yd3 | 39 | 26 | 20 |
Volume is net cylindrical fill. Bag counts round up to whole bags and already include 10% overage, which is the safer field-buying number.
24-Inch Sonotube - Bag Count and Specifications
At 24 inches, each foot of depth contains more than 3 cubic feet of concrete. A single 4-foot pier requires almost half a cubic yard before overage, which makes bagged concrete heavy, slow, and usually more expensive than ready-mix once you factor in labor.
Use the bag counts here for planning, but get a ready-mix quote before buying. On large-diameter piers, one truck often beats a pile of bags even after short-load fees are considered.
24-inch Sonotube bag counts
| Depth | Volume (yd3) | With Overage | 40 lb | 60 lb | 80 lb |
|---|---|---|---|---|---|
| 2 ft | 0.233 yd3 | 0.256 yd3 | 24 | 16 | 12 |
| 3 ft | 0.349 yd3 | 0.384 yd3 | 35 | 24 | 18 |
| 4 ft | 0.465 yd3 | 0.512 yd3 | 47 | 31 | 24 |
| 5 ft | 0.582 yd3 | 0.64 yd3 | 58 | 39 | 29 |
| 6 ft | 0.698 yd3 | 0.768 yd3 | 70 | 47 | 35 |
Volume is net cylindrical fill. Bag counts round up to whole bags and already include 10% overage, which is the safer field-buying number.
What Size Sonotube Do I Need?
Tube diameter is a structural sizing decision, not just a shopping preference. The correct answer depends on the load each pier carries, the spacing between supports, soil capacity, uplift, and the local code path. The table below is a planning guide that helps you narrow the choice before you confirm it with the permit documents or your engineer.
What size Sonotube do I need?
| Application | Recommended Diameter | Typical Depth | Notes |
|---|---|---|---|
| Mailbox post | 6 in | 2-3 ft | Non-structural and light load |
| Fence post (6 ft privacy) | 6-8 in | 2-3 ft | Wind and soil conditions matter |
| Fence post (8 ft or taller) | 8-10 in | 3-4 ft | Use more diameter for gates and high wind |
| Light pergola (up to 10 x 10 ft) | 10 in | 3-4 ft | Verify locally before building |
| Standard pergola | 12 in | 4 ft | Most common DIY choice |
| Residential deck (light) | 10-12 in | 4 ft | Small tributary area only |
| Residential deck (standard) | 12 in | 4 ft | Most common permit path |
| Residential deck (heavy or hot tub) | 14-16 in | 4-5 ft | Loads and spans jump fast |
| Shed footing | 10-12 in | 3-4 ft | Move up for poor soil |
| Carport / RV cover | 14-16 in | 4-5 ft | Wind uplift matters |
| Pavilion / large timber frame | 16-24 in | 4-6 ft | Engineer review recommended |
These are starting-point planning ranges only. Soil, local code, beam spans, uplift, frost depth, and tributary area can all push the required diameter upward.
The concept to keep in mind is tributary area: the portion of deck, roof, or structure whose load flows into a given pier. Bigger tributary area means more load and, in most cases, more required bearing area. That is why jumping from a 10-inch to a 12-inch pier can be the right move even when the post sitting above it looks similar.
- Up to roughly 36 sq ft tributary area per pier often starts in the 10-inch range.
- Roughly 36 to 64 sq ft tributary area per pier is where 12-inch piers become the practical standard.
- About 64 to 100 sq ft tributary area per pier usually pushes projects into 14-inch territory.
- Once the supported area, snow load, or concentrated load grows beyond that, 16-inch and larger piers deserve a code-based or engineered review.
If you want the underlying geometry first, use the How to Calculate Concrete guide and then return here for the diameter-specific bag count. That pairing works well when you are sketching multiple deck layouts and trying to keep the pier count efficient.
How Deep Should a Sonotube Be?
Depth is controlled primarily by frost line and local footing rules. A perfectly sized tube that stops too shallow can still fail. In warm climates, minimum embedment and stability rule the decision. In northern climates, frost depth often decides the full pier length before diameter even enters the conversation.
No Frost / Minimal Frost
Warm-climate projects still need enough depth for stability and local code, but the frost-heave risk is far lower than in northern states.
Minimal frost depth reference
| State / Region | Typical Frost Depth | Typical Minimum Pier Depth | Notes |
|---|---|---|---|
| Florida | 0 in | 12-18 in | No frost concern |
| Hawaii | 0 in | 12 in | - |
| Louisiana | 0 in | 12-18 in | - |
| Mississippi | 0-6 in | 18 in | Rare frost events |
| Alabama | 0-6 in | 18 in | - |
| Georgia | 0-6 in | 18 in | North Georgia runs deeper |
| South Carolina | 0-6 in | 18 in | - |
| Texas (south) | 0-6 in | 18 in | Panhandle deeper |
| Arizona | 0-12 in | 18-24 in | Higher elevations deeper |
| California (south) | 0-12 in | 18-24 in | Mountain zones deeper |
Warm-climate guidance is approximate. Local code can still require deeper footings for wind, expansive soil, or structural reasons.
Moderate Frost
Many central and southeastern states land in the 2 to 3 foot footing conversation, especially away from the warmest coastal zones.
Moderate frost depth reference
| State / Region | Typical Frost Depth | Typical Minimum Pier Depth | Notes |
|---|---|---|---|
| Arkansas | 6-12 in | 24 in | - |
| Tennessee | 6-12 in | 24 in | - |
| North Carolina | 6-18 in | 24 in | Mountains deeper |
| Virginia | 12-18 in | 24-30 in | Mountain counties deeper |
| Kentucky | 12-18 in | 24-30 in | - |
| Missouri | 18-24 in | 30-36 in | - |
| Kansas | 18-24 in | 30-36 in | - |
| Oklahoma | 12-18 in | 24-30 in | - |
| Texas (north) | 12-18 in | 24-30 in | - |
In these markets, a 4-foot pier often covers typical deck work, but the correct answer is still the local jurisdiction, not the state average.
Deep Frost
Northern states and mountain climates can easily push Sonotube depth to 4, 5, or even 6 feet. This is where bag count jumps sharply and tube depth matters as much as diameter.
Deep frost depth reference
| State / Region | Typical Frost Depth | Typical Minimum Pier Depth | Notes |
|---|---|---|---|
| Illinois | 24-36 in | 36-42 in | Chicago area often 42 in |
| Indiana | 24-36 in | 36-42 in | - |
| Iowa | 36-48 in | 42-54 in | - |
| Michigan | 36-48 in | 42-54 in | Upper Peninsula deeper |
| Minnesota | 42-60 in | 48-66 in | Deepest in lower 48 |
| Wisconsin | 36-48 in | 42-54 in | - |
| Ohio | 24-36 in | 30-42 in | - |
| Pennsylvania | 24-36 in | 30-42 in | - |
| New York | 36-48 in | 42-54 in | NYC shallower than upstate |
| New England | 36-60 in | 42-66 in | Northern Maine deepest |
| Colorado | 24-48 in | 30-54 in | Altitude varies sharply |
| Montana | 36-60 in | 42-66 in | - |
| Wyoming | 36-60 in | 42-66 in | - |
| Idaho | 24-48 in | 30-54 in | - |
| Washington | 12-36 in | 18-42 in | West side shallower |
| Oregon | 12-24 in | 18-30 in | East side deeper |
Frost depth is approximate regional guidance. Always verify your required footing depth with the local building department. For permitted deck work, that jurisdiction controls.
This is why the 12-inch by 4-foot pier is common but not universal. In many moderate-frost markets it works well. In Minnesota, northern Wisconsin, northern New England, and other deep-frost climates, a 5 or 6 foot pier is more realistic. That depth increase alone can add several bags per pier even when the diameter does not change.
When your required depth climbs, recalculate the project before you buy materials. A pier that looked like a bagged-concrete job at 4 feet can become a ready-mix decision at 6 feet, especially once you multiply it across a full deck layout.
Sonotube vs. Quik-Tube vs. Generic Tube Forms
Sonotube is the brand name most people search, but the bag-count math does not care whose label is on the cardboard. If the inside diameter is the same, the concrete volume is the same. The differences are practical: availability, coatings, peel-off wrappers, and store inventory.
Sonotube vs. Quik-Tube vs. generic tube forms
| Feature | Sonotube | Quik-Tube | Generic Tube Forms |
|---|---|---|---|
| Brand | Sonoco Products | Quikrete | Various |
| Common diameters | 6-24 in | 6-12 in | Varies by supplier |
| Common lengths | 4, 8, 12 ft | 4, 8 ft | Usually 4 or 8 ft |
| Wall construction | Standard fiber tube | Moisture-resistant coated tube | Varies |
| Peel-away outer wrap | Usually no | Often yes | Sometimes |
| Typical 12 in x 4 ft price | ~$12-$16 | ~$12-$16 | ~$8-$14 |
| Where you see it most | Lumber yards and big-box stores | Big-box stores | Regional lumber yards |
| Concrete yield / bag count | Same by inside diameter | Same by inside diameter | Same by inside diameter |
For estimating concrete, inside diameter is what matters. If the tube is labeled 12 inches, the bag count is the same regardless of brand. Practical differences are availability, coating, and how easily the form strips off after curing.
In other words, the question is rarely “Which brand uses fewer bags?” The real question is which tube is available in the diameter you need, in good condition, at a store close enough that transport and damage are not a hassle. For estimating, diameter wins; brand comes second.
If you are pairing tube forms with other shapes in the same job, the full Concrete Calculator can help you total slabs, footings, and tube sections together instead of estimating them piecemeal.
How to Set a Sonotube and Pour Concrete
Installing tube forms is straightforward when the sequence is right. Most problems are not math problems at all. They are setup problems: shallow holes, crooked forms, missing bracing, or anchors that were never staged before the pour began.
Step 1 - Dig the hole
Dig to the required frost depth plus any local extra depth requirement. Make the hole a little wider than the tube so you can adjust alignment and compact backfill around it. If the design calls for a wider bearing pad or bell, create that geometry before the tube is set.
Step 2 - Set and plumb the tube
Place the tube in the hole, trim it to final height, and check plumb in two directions. Backfill around the sides and tamp in lifts so the form stays put while you pour. Tall tubes above grade usually need temporary 2x4 bracing.
Step 3 - Mix or stage the concrete
Calculate the total bag count first so the full pour is staged before you start. Standard concrete should be mixed to the manufacturer's water ratio. Fast-setting post mix can be useful for simple posts, but most structural pier work benefits from consistent mixed concrete.
Step 4 - Pour in lifts and rod the mix
Fill the tube in manageable lifts, usually 6 to 8 inches at a time, and rod or tap each lift to release trapped air. This keeps voids out of the pier and helps the mix settle around anchor bolts or rebar.
Step 5 - Set hardware while the concrete is plastic
Post bases, J-bolts, and anchor hardware need to go in before the concrete reaches initial set. Layout lines, templates, and measurement checks should be ready before the final lift is placed.
Step 6 - Cure and strip the form if needed
Protect the fresh pier from early drying and give it at least a day or two before light loading. If you want exposed concrete above grade, score and peel the cardboard after the mix has hardened enough to hold its surface cleanly.
If you still need to check the concrete quantity from raw dimensions, run the Tube Calculator directly or use the broader bag-count guide for side-by-side bag-size comparisons.
Common Sonotube Mistakes to Avoid
The bag count can be perfect and the pier can still underperform if the install sequence is sloppy. These are the mistakes that cause the most preventable rework on residential tube-form projects.
Mistake 1 - Stopping above the frost line
This is the classic pier failure. If the footing ends above local frost depth, freezing soil can heave the pier upward and rack the structure above it. Depth is not decorative; it is structural.
Mistake 2 - Using the wrong diameter in the math
Tube volume is based on the labeled inside diameter. Measuring the outside of the cardboard or guessing from memory can swing the result enough to leave you short on bags, especially at larger diameters.
Mistake 3 - Not bracing the form before the pour
Fresh concrete is heavy. A tall unbraced tube can drift out of plumb, twist, or settle when the concrete starts loading the form. Backfill and brace first, then pour.
Mistake 4 - Adding too much water
Loose, soupy mix is easier to place but weaker and more shrink-prone. Stick to the bag or mix design water range and improve workability with mixing discipline, not extra water.
Mistake 5 - Waiting too long to set anchors
Anchor bolts and post bases need to be aligned while the concrete is still plastic. If you pause to hunt for hardware after the pour, the working time can disappear fast.
Mistake 6 - Buying exactly the theoretical bag count
Tube forms are simple shapes, but field conditions are not perfect. Add the 10% overage, round up, and keep the project moving. The cost of one extra bag is tiny compared with a mid-pour store run.
Frequently Asked Questions
These are the most common Sonotube size, depth, and bag-count questions from homeowners planning deck piers, pergolas, fence posts, and similar residential footing work.
How many bags of concrete do I need for a 12-inch Sonotube?+
A 12-inch Sonotube needs 6 bags of 80 lb concrete mix at 4 feet deep when you include the standard 10% overage. At 3 feet deep it needs 5 bags, and at 5 feet deep it needs 8 bags. That 12-inch by 4-foot combination is the most common residential deck-pier setup.
What size Sonotube do I need for a deck?+
For most standard residential decks, 12 inches is the practical default. Lighter decks with small tributary areas may be approved at 10 inches, while heavier decks, hot tub platforms, or wide beam spacing often push projects into 14 or 16 inches. The permitting authority and the actual pier load decide the final answer.
How deep should a Sonotube be for a deck?+
A deck pier has to extend below the local frost line. In many U.S. markets that means roughly 4 feet. In warm climates it may be shallower, and in deep-frost states it may need to be 5 to 6 feet. The local building department is the correct source for the minimum permitted depth.
Can I use fast-setting concrete in a Sonotube?+
You can, especially for simple post-setting work, but structural pier projects usually benefit from consistent mixed concrete and controlled placement. Fast-setting mixes reduce working time, which can be a disadvantage if you still need to set anchors accurately.
What is the difference between Sonotube and Quik-Tube?+
They are competing brands of round tube forms. For estimating concrete, the key point is that equal inside diameter means equal concrete volume. The bag count does not change by brand. The real differences are availability, coatings, peel-off wrappers, and store selection.
Is bagged concrete or ready-mix better for large Sonotubes?+
Bagged concrete is convenient for small and moderate tube pours, but once diameter or quantity climbs, ready-mix often becomes the better choice. Large 18-inch and 24-inch piers are the clearest examples because the labor of mixing dozens of bags becomes part of the job cost.
How many bags do I need for a 10-inch Sonotube?+
At 4 feet deep, a 10-inch Sonotube needs 4 bags of 80 lb mix with overage. At 3 feet it needs 3 bags, and at 6 feet it needs 6 bags.
How many bags do I need for an 8-inch Sonotube?+
At 4 feet deep, an 8-inch Sonotube needs 3 bags of 80 lb mix with overage. At 3 feet it needs 2 bags, and at 6 feet it needs 4 bags.
Related Guides and Calculators
Use these related guides when you need to move from tube-specific bag counts into general concrete math, project pricing, or calculator workflows for mixed-shape pours.
How Many Bags of Concrete Do I Need?
Bag-count tables for slabs, footings, columns, and post holes across the common 40, 60, 80, and 90 lb bag sizes.
Read guide ->How to Calculate Concrete
Step-by-step formulas for slabs, footings, walls, columns, and other common pours, with worked examples and conversion tables.
Read guide ->Concrete Cost Per Yard
Use current ready-mix price benchmarks to decide when bagged concrete stops making sense for larger pier projects.
Read guide ->Tube Calculator
Calculate tube-form volume and bag counts by diameter, depth, and quantity, with overage built in.
Open Tube Calculator ->Bag Calculator
Convert cubic volume into 40, 60, 80, and 90 lb bag counts and compare the tradeoff between bag sizes.
Open Bag Calculator ->Concrete Calculator
Use the full calculator when your project combines slabs, footings, or wall sections with the tube work.
Open Concrete Calculator ->Know your bag count before you leave for the store.
Use the free ConcreteCalc Pro tube calculator to turn diameter, depth, and pier count into an exact concrete shopping list with overage already included.