Concrete Math Pro is a free concrete calculator for homeowners and contractors in the United States. It tells you how much concrete to order for a slab, footing, wall, post hole, set of steps or curb, in cubic yards and in bags.
Why this site exists
Most concrete calculators give you one number and leave the rest to you. This one gives the whole order on one screen: volume, four bag sizes, the ready-mix quantity rounded the way suppliers sell it, weight and cost. It also draws your pour to scale, so you can see a wrong measurement before you buy.
How the numbers are checked
Every formula and every constant used by the calculator is listed on the How We Calculate page, with its source. The calculator is tested against worked examples each time it changes.
What it is not
The calculator estimates quantities. It does not design structures. Footing sizes, slab thickness for vehicles and reinforcement for structural work are set by your local building code and, where required, an engineer.