How Does This Calculator Work?
The calculator first finds the slab's volume in cubic feet (length × width × thickness, converting thickness from inches to feet), then divides by 27 — the number of cubic feet in a cubic yard, since ready-mix concrete is priced and delivered by the cubic yard.
Ordering concrete by the truckload means getting your volume estimate right — order too little and you'll have a costly delay mid-pour; order too much and you're paying for waste. This calculator converts your slab dimensions into cubic yards, the unit ready-mix concrete is sold in.
Example Calculation
Patio Slab Example
A 20 ft × 10 ft patio, 4 inches thick.
(20 × 10 × (4/12)) ÷ 27 ≈ 2.47 cubic yards.
Tips
Always add 5–10% to your final order to account for spillage, uneven subgrade, and form deflection — most concrete suppliers recommend this as standard practice.