This concrete volume calculator finds how much concrete you need for any rectangular slab, footing, or pad. Enter length, width, and thickness above to get the volume in cubic yards, cubic feet, and pre-mixed bags.
How to use this calculator
- Enter length and width in feet.
- Enter thickness in inches.
- Read the cubic yards and bag count.
How is concrete volume calculated?
Volume (ft³) = Length × Width × (Thickness ÷ 12) Cubic yards = Volume (ft³) ÷ 27
- Thickness ÷ 12 — converts inches to feet
- 27 — cubic feet per cubic yard
Example calculation
For a 10 ft × 10 ft pad, 4 inches thick:
- Volume = 10 × 10 × (4 ÷ 12) = 33.3 ft³
- Cubic yards = 33.3 ÷ 27 = 1.23 yd³
- Add 10% waste → order about 1.35 yd³
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Frequently Asked Questions
How do I calculate concrete volume?
Multiply length by width by thickness in feet, then divide by 27 to convert cubic feet to cubic yards, which is how concrete is ordered.
How many cubic feet are in a cubic yard?
There are 27 cubic feet in one cubic yard, since a cubic yard is 3 feet on every side (3 x 3 x 3).
How much extra concrete should I order?
Add 5 to 10 percent to cover spillage, uneven subgrade, and over-excavation, and always round up to the nearest quarter yard.