Calculator
Concrete Calculator
Enter slab dimensions to get cubic yards, bag counts and an estimated delivered cost.
Model reviewed August 2026
Concrete needed
5.43 cubic yards
Includes 10% overage
- Cubic feet
- 133.3
- 80 lb bags
- 245 bags
- 60 lb bags
- 326 bags
- Ready-mix cost estimateDelivered, excludes labor and forms
- $896 – $1,277
Estimates only. Local pricing, site conditions and code requirements change the real number.
The formula
Cubic yards = (length x width x thickness in feet) / 27, plus a 10% overage allowance
There are 27 cubic feet in a cubic yard. An 80 lb bag yields about 0.6 cubic feet, and a 60 lb bag yields about 0.45 cubic feet.
Worked example
A 20 ft x 20 ft slab at 4 inches thick is 133 cubic feet, or 4.9 cubic yards with 10% overage — roughly $900 to $1,200 delivered.
Frequently asked questions
How many bags of concrete in a yard?
About 45 eighty-pound bags or 60 sixty-pound bags make one cubic yard. Anything over roughly one cubic yard is usually cheaper and easier as ready-mix delivery.
How thick should a concrete driveway be?
Five inches is standard for residential driveways on a compacted base; six inches if you park heavy vehicles or an RV.
Sources
Sources & verification
- ACI concrete practice and yield guidance
- NRMCA ready-mixed concrete yield data
- International Residential Code — concrete (R402/R506)
- International Code Council (IRC/IBC)
Model vintage August 2026. The links above are the issuing agencies' own pages — we publish them so you can confirm the current rule yourself, not as evidence that each fact on this page was re-checked with them today. Cost figures are modeled estimates based on national baselines adjusted for local labor and material pricing, not quotes. Permit rules change; confirm with the building department before starting work.