Free Estimator
Find out exactly how many bags of concrete you need for any project volume, in any bag size.
Use this free concrete bag calculator to convert cubic yards or cubic feet into bag counts for 40 lb, 60 lb, 80 lb, and 90 lb concrete mix bags. Works with all major brands including Quikrete, Sakrete, and generic store-brand mixes. Enter your project volume directly, or enter your slab, footing, or column dimensions and let the calculator compute the volume first, then get a full bag comparison table updated in real time.
All Bag Sizes Covered — Compare 40 lb, 60 lb, 80 lb, and 90 lb bag counts side by side.
Enter Volume or Dimensions — Input cubic yards directly, or calculate from length, width, and thickness on the spot.
10% Overage Built In — Recommended waste buffer automatically included in every estimate.
Brand Yield Reference — Quikrete, Sakrete, and generic yields per bag included for accurate comparison.
PDF Export & Share Link — Save or share your bag estimate with your crew or supplier.
Calculator Section
Enter your project volume below to get a full bag count comparison across all standard bag sizes. If you do not know your volume yet, switch to the Dimensions tab to calculate it from length, width, and thickness. For a full concrete estimate with 3D preview, use the concrete calculator or the concrete slab calculator.
Figuring out bag count comes down to two steps: calculate your project volume in cubic yards, then divide by the yield of your chosen bag size. The sections below show the formula, a step-by-step workflow, and a yield reference table for all standard bag sizes so you can double-check the calculator output before you head to the store.
Step 1 - Calculate volume Volume (yd3) = Length (ft) x Width (ft) x Thickness (ft) / 27 Step 2 - Add 10% overage Order Volume = Volume x 1.1 Step 3 - Divide by bag yield Bags Needed = Order Volume / Yield per bag Example (80 lb bags) A 12 ft x 10 ft slab at 4 inches thick: Volume = 12 x 10 x (4 / 12) / 27 = 1.48 yd3 (with 10%) Bags = 1.48 / 0.022 = 67 bags of 80 lb mix
Measure the project and convert it to cubic yards before you estimate bags. Slabs use length times width times thickness, footings use length times width times depth, and round columns use pi times radius squared times height. If your volume is already in cubic feet, divide by 27 to convert to cubic yards, which is the standard planning unit for concrete.
Always add about 10% to the base volume before you convert to bags. That buffer covers spillage, uneven subgrade, small variations in form size, and minor measurement errors. Skipping overage is the fastest way to run short of mix partway through a pour, especially on DIY jobs where bag yields vary slightly with water content and mixing consistency.
Pick the bag size that matches both the project and the crew handling the material. Eighty pound bags are the most common residential choice because they balance yield and availability. Forty and sixty pound bags are easier to move for one person, while ninety pound bags reduce the total number of bags you need at the cost of heavier lifting.
Take the order volume, including overage, and divide it by the yield of the selected bag size. Standard planning yields are 0.011 yd3 for 40 lb bags, 0.017 yd3 for 60 lb bags, 0.022 yd3 for 80 lb bags, and 0.025 yd3 for 90 lb bags. Always round up to the next whole bag because partial bags are not practical in the field.
Most standard bagged mixes from Quikrete and Sakrete have very similar yields for the same bag weight, but fast-setting and specialty mixes can vary. Check the yield printed on the label if you are buying a high-strength, fiber-reinforced, or fast-setting product. If the printed yield differs from the standard reference values, use the printed number when you finalize the order.
| Bag Size | Yield per Bag (ft³) | Yield per Bag (yd³) | Bags per yd³ | Notes |
|---|---|---|---|---|
| 40 lb | 0.30 ft³ | 0.011 yd³ | ~90 | Good for small repairs |
| 60 lb | 0.45 ft³ | 0.017 yd³ | ~60 | Popular for fence posts |
| 80 lb | 0.60 ft³ | 0.022 yd³ | ~45 | Most common residential size |
| 90 lb | 0.68 ft³ | 0.025 yd³ | ~40 | Fewer bags, heavier to lift |
| 50 lb fast-set | 0.375 ft³ | 0.014 yd³ | ~72 | Quikrete Fast-Setting |
| 80 lb fast-set | 0.60 ft³ | 0.022 yd³ | ~45 | Same yield, faster cure |
Not all concrete bags are the same. Yield per bag varies by weight, brand, and mix type. Use this comparison to choose the right bag size and brand for your project before you calculate your final order quantity.
Quikrete is the most widely available concrete mix brand in the United States and is stocked at most major home improvement retailers. Standard Quikrete Concrete Mix is widely used for slabs, footings, posts, and general concrete repair work.
Best for: Slabs, footings, posts, and general flatwork.
Quikrete Fast-Setting Concrete Mix is designed for post-setting and other quick-turn applications. You can place it directly in the hole and add water on top, which makes it a popular option for fence posts, sign posts, and mailbox bases.
Best for: Fence posts, mailbox bases, and sign posts.
Sakrete is a common alternative to Quikrete in many markets and offers comparable yields for standard bag sizes. It is used for the same broad range of residential and light commercial pours, including slabs, footings, columns, and repairs.
Best for: Slabs, footings, columns, and structural pours.
Forty pound bags are the lightest standard option and are easiest to carry, move, and mix without help. The tradeoff is that they produce the lowest yield per bag, so the total bag count climbs quickly on anything larger than a small repair.
Best for: Small repairs, edging, and projects where lifting weight is the main constraint.
Sixty pound bags strike a practical middle ground between manageable weight and useful yield. They remain popular for fence posts, deck piers, and smaller residential pours where eighty pound bags feel too heavy for repeated mixing.
Best for: Fence posts, deck piers, and small slabs under about 0.5 yd³.
Eighty pound bags are the default choice for many homeowners and contractors because they offer the best balance of availability, yield per bag, and cost efficiency. Most residential bag-count rules of thumb assume an 80 lb bag as the baseline reference size.
Best for: Patios, driveways, garage floors, footings, columns, and general residential flatwork.
These bag calculator FAQs cover bag yields, brand comparisons, overage rules, fast-setting mixes, cost estimates, and when to switch from bags to ready-mix concrete. The first two answers are expanded by default.
The number of bags depends on your project volume and the bag size you choose. First calculate the volume in cubic yards, add about 10% for overage, and then divide by the yield of the selected bag size. For a 10 x 10 foot slab at 4 inches thick, the volume is about 1.23 yd3 before overage and about 1.35 yd3 after overage, which takes roughly 62 bags of 80 lb mix.
One cubic yard of concrete takes about 45 bags of standard 80 lb mix, based on a yield of roughly 0.022 yd3 per bag. If you include a 10% order buffer, the working rule becomes about 50 bags of 80 lb mix per cubic yard ordered. That makes 80 lb bags the most common reference point when people compare bagged concrete to ready-mix for residential pours.
Fence post bag counts depend on the diameter and depth of the hole as well as the total number of posts. A common 8-inch diameter hole that is 2 feet deep needs about 0.026 yd3 of concrete, which is a little over one 80 lb bag. Once you account for waste, many installers plan on roughly 1.3 bags per post for that size hole or two 60 lb bags when using a lighter mix size.
A standard 80 lb bag of concrete mix yields about 0.60 cubic feet, which is roughly 0.022 cubic yards. That figure is commonly used for Quikrete 80 lb Concrete Mix, Sakrete 80 lb Concrete Mix, and similar standard concrete blends from major retailers. Specialty mixes can vary slightly, so the printed bag label should take priority when you are finalizing a large order.
For pours below roughly 1 cubic yard, bagged concrete is often more practical because ready-mix suppliers usually charge a minimum delivery fee even for small orders. Between about 1 and 3 cubic yards, the economics depend on local pricing and labor availability. Once the job gets beyond a few cubic yards, ready-mix is usually cheaper per yard and dramatically faster than hauling, mixing, and placing dozens of individual bags.
A 10 x 10 foot slab at 4 inches thick contains about 1.23 cubic yards of concrete before waste and about 1.35 cubic yards after adding a 10% buffer. That works out to roughly 62 bags of 80 lb mix, about 80 bags of 60 lb mix, or roughly 122 bags of 40 lb mix. If the slab is thicker than 4 inches, the required bag count increases quickly, so exact dimensions matter.
Quikrete and Sakrete are the two most common bagged concrete brands in the United States, and their standard mixes have very similar yields for the same bag weight. The biggest practical differences are local availability, retailer distribution, and the specific specialty lines each brand offers. For ordinary standard mix, both brands are suitable for slabs, footings, columns, and repair work as long as the yield printed on the bag matches your estimate.
Post-hole requirements vary by hole diameter and depth, but the principle is always the same: calculate the cylindrical volume, add overage, and divide by the bag yield. A 6-inch hole 2 feet deep may use around half of an 80 lb bag, while an 8-inch hole 2 feet deep is closer to 1.2 bags and a 10-inch hole 3 feet deep can move above 2 bags. Always round up and then add a little extra for multi-post projects.
Related Tools
Use these related calculators to get the full project volume before converting to bag counts, or to estimate cost once you have your bag count.
The all-in-one concrete calculator for slabs, footings, columns, walls, and stairs. Get your project volume first, then use the bag calculator to convert to bags.
Open CalculatorCalculate exact concrete volume for rectangular and circular slabs. Includes bag counts, 10% overage, rebar estimate, and cost guidance built in.
Open CalculatorEstimate total material cost once you have your bag count or cubic yardage. Includes ready-mix and bagged concrete pricing by project type.
Open Calculator