Concrete calculator
Enter your slab, footing, wall, or column and get the cubic yards, the number of 40/60/80 lb bags, and ready-mix cost. Plus a gravel, sand, topsoil, and mulch calculator. Free, instant, no signup.
Includes a 10% waste allowance. Thickness/depth/diameter are in inches.
Concrete by slab size
Frequently asked questions
How do I calculate how much concrete I need?
Multiply length × width × thickness (all in feet) to get cubic feet, then divide by 27 for cubic yards. A 10×10 ft slab at 4 inches thick is about 1.23 cubic yards. The calculator does this for slabs, footings, walls, and round columns, and adds a 10% waste allowance.
How many bags of concrete are in a cubic yard?
A cubic yard is 27 cubic feet. An 80-lb bag yields about 0.6 cubic feet, so it takes about 45 80-lb bags, 60 60-lb bags, or 90 40-lb bags to make one cubic yard. Above roughly one yard, ready-mix is usually cheaper than bags.
How much does a yard of concrete cost?
Ready-mix concrete typically runs about $120–$180 per cubic yard delivered, before short-load or delivery fees. Enter a price per yard in the calculator to estimate your total, including the waste allowance.
How much gravel or mulch do I need?
Multiply the area in square feet by the depth in feet, then divide by 27 for cubic yards. The Gravel & aggregate tab also converts yards to tons using each material’s density, since bulk gravel, sand, and stone are usually sold by the ton.