Concrete Thickness Calculator

Why This One Is Different

Pick the wrong thickness and you either pour a driveway that cracks under a delivery truck or a sidewalk with material you didn't need to buy. Thickness is the single input that swings a concrete order the most. A slab poured at 4-1/8 inches instead of a planned 4 inches isn't a rounding error; that eighth of an inch alone shifts total volume by roughly 3%, which is why a measured thickness, not a number pulled from memory, belongs in the field below. This calculator lets you compare thickness options side by side and see the yardage difference before concrete is on the truck.

Where the Numbers Come From

• A 1/8" thickness variation on a 4" slab is approximately a 3% swing in total volume, since thickness error compounds faster than length or width error on typical slabs. Source: NRMCA CIP 8 convention, applied via construction-estimating engine
• 4-inch slabs are a common trade default for walkways and patios, and 5-6 inches for driveways carrying vehicle loads. This is a trade convention, not a code minimum, and local code or soil conditions can require more. Source: trade convention, labeled as such (not codified in a standard)
• Order 4-10% more concrete than your plan-derived volume no matter which thickness you settle on, since form deflection and subgrade irregularity affect every pour the same way, per NRMCA guidance. Source: NRMCA, CIP 8, Discrepancies in Yield (2021 reprint)