Concrete Calculator
Work out exactly how much concrete you need for a slab, patio, footing or shed pad - in cubic feet, cubic yards, and the number of 40/60/80 lb bags.
How to use this concrete calculator
Measure the length and width of your pour in feet and its depth in inches. Pick your waste allowance (5% is standard) and the bag size you plan to use. The calculator converts everything to cubic yards and tells you how many bags to buy - or whether it is worth ordering a ready-mix truck instead.
As a rule of thumb, anything over about 1 cubic yard (45+ bags) is usually cheaper and less back-breaking with a concrete delivery. If you are mixing by hand, rent a mixer for anything bigger than a handful of bags.
Concrete calculator FAQ
How thick should a concrete slab be?
4 inches for patios and walkways, 4-6 inches for shed and garage floors, and 8-12 inches for driveways or load-bearing footings. Reinforce with rebar or wire mesh on thicker slabs.
How many cubic feet is in a cubic yard?
27 cubic feet (3 x 3 x 3). To convert, divide the volume in cubic feet by 27.
How much does a cubic yard of concrete cost?
Ready-mix concrete typically costs $130-$180 per cubic yard in the US (2025-2026 prices), with a delivery minimum fee on top. Bags of mix usually cost more per yard but avoid the minimum.