Concrete Calculator
How much concrete do I need? Enter slab dimensions to get cubic yards, a waste-adjusted volume, a recommended order quantity, and an optional cost estimate.
Calculator
How it works
We convert every dimension to feet, multiply length x width x thickness x quantity for cubic feet, then divide by 27 to get cubic yards. Waste is applied after that conversion. Recommended order rounds up to the next 0.25 cubic yard so you are less likely to run short.
Formula
Cubic feet = L x W x T x quantity (all in feet). Cubic yards = cubic feet / 27. With waste = cubic yards x (1 + waste%). 1 cubic yard = 27 cubic feet.
Example
A 10 ft x 12 ft slab, 4 inches thick, quantity 1, 10% waste: 10 x 12 x (4/12) = 40 cubic feet ~ 1.48 cubic yards exact; with waste ~ 1.63; recommended order 1.75 cubic yards.
How to measure
Measure length and width of the pour area. Measure thickness at the planned slab depth (often 4 inches for a patio). Use the same units consistently, or mix feet and inches—the calculator converts them.
FAQ
What is a concrete calculator?
It estimates the volume of concrete for a slab from length, width, thickness, and quantity, then adds waste so you can order ready-mix or bags with a buffer.
How much extra concrete should I order?
A 10% waste factor is a common default for slabs. Increase it for irregular shapes, pumping, or if the subgrade is uneven.
Why is recommended order higher than the exact volume?
Ready-mix is typically ordered in quarter-yard steps, and shorting a pour is expensive. We round up after waste.