Concrete Calculator
Work out how many cubic yards of concrete you need for a slab, patio or footing, and how many bags that is.
Concrete calculator
How it is calculated
Find the volume in cubic feet, then divide by 27 to get cubic yards, because a cubic yard is 3 ft × 3 ft × 3 ft.
Cubic yards = length (ft) × width (ft) × thickness (in) ÷ 12 ÷ 27Example: a 10 × 10 ft slab 4 in thick is 100 × 4 ÷ 12 = 33.3 ft³ = 1.23 yd³. Adding 10% gives 1.36 yd³, so order 1.5 yd³.
For bags, one 80 lb bag makes about 0.6 ft³, so a cubic yard is roughly 45 bags.
Common questions
How many cubic yards of concrete are in a truck?
A ready-mix truck typically carries up to about 10 cubic yards. Ask your supplier for the exact load and any short-load fee on small orders.
How thick should a concrete slab be?
Patios and walkways are commonly 4 inches. Driveways are often 5 to 6 inches. Check with your contractor or local code.
How many 80 lb bags make a cubic yard?
About 45 bags of 80 lb concrete mix make one cubic yard (27 ft³ ÷ 0.6 ft³ per bag).