How Much Extra Concrete to Order

NRMCA's CIP 31: “Quantity of concrete ordered should be 4% to 10% more than an estimate calculated from the plan dimensions to account for contingencies.” For a 10 × 10 ft slab 4 in thick (1.23 cu yd), that means ordering 1.28 to 1.36 cu yd, or 58 to 62 bags of 80 lb Quikrete Concrete Mix.

Set up for: a slab with an over-order margin · Different project?

FAQ

How much extra concrete should I order?

NRMCA suggests 4% to 10% more than the estimate from the plan dimensions, for uneven ground, form bulges and spills.

Does the bag count include extra?

The calculator shows both: the whole bags for the exact volume and the count with the margin you pick (none, 4, 5, 7 or 10%).

Sources

Volumes only. ConcreteMath calculates volumes, bag counts, weights and your own cost figures. It gives no structural or engineering advice and never sizes footings, piers, slabs or rebar: those come from your plans, an engineer or your local building department. Bag counts are estimates from each maker's published yield; actual use varies with hole shape, uneven ground, waste and mixing. Bulk weights are published ranges; your supplier's figure wins.