Free Concrete CalculatorVolume, Bags & Cost

For a rectangular slab, footing, or wall, use: Volume (yd³) = Length (ft) × Width (ft) × Thickness (ft) ÷ 27. Convert thickness from inches to feet by dividing by 12. For a 10 × 12 ft patio at 4 inches thick: 10 × 12 × 0.333 ÷ 27 = 1.48 yd³. Always add 10% overage to your order: 1.48 × 1.1 = 1.63 yd³. For round columns, stairs, and other shapes, use the dedicated calculator above — each one applies the correct formula automatically.

The number of bags per cubic yard depends on bag size: 40 lb bags: approximately 90 bags per cubic yard; 60 lb bags: approximately 60 bags per cubic yard; 80 lb bags: approximately 45 bags per cubic yard; 90 lb bags: approximately 40 bags per cubic yard. These counts are based on standard concrete mix yields. Fast-setting mixes can have a slightly different yield, so check the bag label. Use the Concrete Bag Calculator above to get an exact count for your project volume.

The 10% overage rule means ordering 10% more concrete than your calculated volume to account for form deflection, uneven subgrade, spillage, and minor measurement errors. For a 2.0 yd³ calculated volume, order 2.2 yd³. This buffer is standard practice in the concrete industry and is built into every estimate on ConcreteCalc Pro. Running short on a concrete pour is far more costly than having a small amount left over — a cold joint caused by stopping and restarting a pour is a structural defect that is expensive to repair.

One cubic yard equals 27 cubic feet (3 ft × 3 ft × 3 ft). Ready-mix concrete in the United States is ordered and priced in cubic yards. Bagged concrete yields are listed on the bag in cubic feet. To convert: divide cubic feet by 27 to get cubic yards, or multiply cubic yards by 27 to get cubic feet. ConcreteCalc Pro displays results in both cubic yards and cubic meters simultaneously, and handles all unit conversions automatically when you switch between Imperial and metric mode.

Yes. ConcreteCalc Pro is used by homeowners, contractors, and construction professionals for projects of all sizes. The calculators support all standard pour types — residential slabs, commercial footings, round columns, retaining walls, stairways, cylindrical piers, tube forms, and curb and gutter sections. For large commercial projects, use the Pin Baseline feature to save and compare multiple scenarios, and the PDF export to share estimates with your team or client.

Yes. All calculators on ConcreteCalc Pro are completely free to use with no account and no subscription. Every feature — including real-time previews, PDF export, share links, and unit conversion — is available at no cost. The site may be supported by advertising, but the core tools remain free to access.