Material Calculator for a Concrete Slab

Why This One Is Different

Concrete is the headline material on a slab job, but it's rarely the only line on the shopping list: vapor barrier, wire mesh or rebar, and edge-form lumber all get bought around the same trip. This calculator handles the concrete side precisely: plan volume from your dimensions, an ordering allowance for spillage and subgrade irregularity, and, if you're buying bags instead of ready-mix, a whole-bag count at the published yield for a 60 lb mix (0.45 cubic feet per bag, or about 60 bags per cubic yard). What it won't do is guess at your reinforcement schedule, because that's a structural decision, not a volume calculation.

Where the Numbers Come From

• Bag count per yard isn't a round number by accident: a 60 lb bag of concrete mix yields approximately 0.45 cubic feet, giving roughly 60 bags per cubic yard, a published, manufacturer-stated 'approximately' figure, not an exact number. Source: QUIKRETE Concrete Mix No. 1101 TDS (rev. 2022)
• Order more than your raw plan volume, no matter how carefully you measured: NRMCA guidance is to order 4-10% more than plan-derived volume for any formed pour, applied on top of the raw bag count before rounding to whole bags. Source: NRMCA, CIP 8: Discrepancies in Yield (2021 reprint)
• Rounding follows net volume, then the ordering allowance, then rounds up to the nearest whole purchase unit. Partial bags aren't sold, so the calculator never reports a fractional bag count. Source: construction-estimating engine convention (QUIKRETE TDS 'approximately' basis)