Concrete Slab Calculator: Cubic Yards & Cubic Feet
Estimate concrete slab volume in cubic yards and cubic feet using feet-and-inches dimensions, thickness in inches, and an adjustable extra allowance. All measurements use US customary units. Defaults are examples; use actual site dimensions and product coverage.
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Results update live as you type. Estimates only — not financial, tax, or investment advice.
The Formula
Volume ft³ = Area ft² × thickness inches ÷ 12; yd³ = ft³ ÷ 27
Understanding the Concrete Slab Calculator: Cubic Yards & Cubic Feet
Example: a 20 by 10 foot slab at 4 inches thick needs 66.67 cubic feet, or 2.469 cubic yards. Adding 10% gives 2.716 cubic yards before supplier order rounding.
This estimates uniform rectangular slab volume only. It does not select slab thickness or account for thickened edges, footings, reinforcement or subgrade variation. Use your project specifications for thickness and add separately measured footings. Confirm delivery increments with your supplier.
One cubic yard is 27 cubic feet. Convert slab thickness from inches to feet before multiplying. Order volume is not rounded to a delivery increment: your supplier may sell in specific increments or charge for small loads.
Frequently Asked Questions
How do I measure an irregular area?
Split it into non-overlapping rectangles, calculate each separately, and add the base quantities. Apply your extra allowance once to the total.
What does the extra allowance cover?
The percentage adds material for cuts, uneven surfaces, settling or handling losses. It is adjustable and is not a universal recommendation. Confirm your order with your supplier.
Does this include footings or thickened edges?
No. This model is a rectangular slab of uniform thickness. Measure other concrete volumes separately and avoid counting overlapping volumes twice.