Concrete slab calculator
Enter the length, width, and depth of your slab. This tool gives you the cubic yards of ready-mix concrete to order, plus a 10 percent waste allowance for spillage and an uneven subgrade.
Your dimensions
Cubic yards to order
1.6
Estimated ready-mix cost: $244 to $326
Prices are typical ranges as of June 2026. Your local price will vary.
Assumptions
- •Slab is a simple rectangle; irregular shapes should be split into rectangles and added together.
- •Depth is measured in inches, length and width in feet.
- •Ready-mix concrete price range is a typical delivered range and excludes pump fees.
Questions this calculator answers
How many cubic yards of concrete do I need for a 10x12 slab?
About 1.6 cubic yards for a 4 inch thick slab, including a 10 percent waste allowance. That comes from 10 ft x 12 ft x 4 in of depth, which is 40 cubic feet before waste, or 1.481 cubic yards. Most ready-mix suppliers sell in quarter-yard increments and round up, so you would order 1.5 or 2 yards.
How thick should a concrete slab be?
4 inches for a patio, walkway, or shed floor. 5 to 6 inches for a driveway that carries cars. Thicker slabs cost more concrete but resist cracking under vehicle weight and freeze-thaw cycles.
Why does the calculator add 10 percent extra?
To cover spillage, an uneven subgrade, and small measurement error. Ready-mix trucks charge for a minimum load and short-load fees if you run out mid-pour, so a small buffer is cheaper than a second delivery.
Should I order ready-mix or mix my own bags for a slab this size?
Ready-mix delivery is usually cheaper past about 1 cubic yard, since a truck load covers it in one pour with consistent quality. Under a cubic yard, mixing bags is often more practical. Use the concrete bags calculator to compare.
Does this estimate include rebar or a gravel base?
No. This tool estimates concrete volume only. A compacted gravel base under the slab and rebar or wire mesh inside it are common for durability, but they are priced and ordered separately.