Concrete Calculator
Order the right concrete, the first time.
Concrete Calculator
Volume (cu yd) = Length x Width x Thickness / 27
Calculated instantly
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What This Calculator Does
The Concrete Calculator estimates the concrete needed for a slab in cubic yards and the number of pre-mixed bags required. It prevents both under-ordering mid-pour and over-ordering that wastes money.
How It Works
The slab volume in cubic feet is length times width times thickness in inches divided by 12. Dividing by 27 converts to cubic yards, then bag counts follow from each bag size yield.
Example
A 10 x 8 foot slab at 4 inches thick needs 10 x 8 x 0.333 / 27 = 0.99 cubic yards, or about 58 sixty-pound bags.
Formula
Volume (cu yd) = L × W × (Thickness in / 12) / 27Bags = Volume / Yield per Bag60 lb ≈ 0.017 cu yd, 80 lb ≈ 0.022 cu yd.
Reading the Results
Volume Needed
The concrete volume for your slab in cubic yards, the unit used when ordering a delivery.
60 lb / 80 lb Bags
How many pre-mixed bags to buy if you are mixing by hand, by bag size.
Frequently Asked Questions
How much concrete do I need for a slab?
Multiply length by width by thickness in feet and divide by 27 for cubic yards. The calculator automates this and reports bag counts.
How many bags of concrete are in a cubic yard?
Roughly 59 sixty-pound bags or 45 eighty-pound bags per cubic yard, accounting for standard yields.
Should I order extra concrete?
Order 5-10% extra. Slight over-excavation and spillage are common, and running short mid-pour is far worse than having a little left.