How it works
How to calculate it
The calculator applies the values you enter to this formula:
Cubic yards = length × width × (depth ÷ 12) ÷ 27 × (1 + extra rate).
How to use this calculator
- Measure the pour in separate rectangular sections.
- Enter the finished concrete depth in inches.
- Add an allowance and the supplier's price per cubic yard.
Worked example
A 20 × 15 ft slab, 4 inches thick, is about 3.7 cubic yards before the extra allowance.
Important assumptions
- Dimensions describe a uniform rectangular pour.
- Subgrade, reinforcement, delivery, short-load fees, and labor are excluded.
- Confirm the order with the concrete supplier.
Common mistakes to avoid
- Multiplying inch depth as though it were feet.
- Ignoring thickened edges, footings, or uneven excavation.
- Ordering exactly the geometric volume with no field allowance.
Method reviewed June 10, 2026. Prices and rates are user-provided defaults and should be replaced with local values.