How to use this calculator
- Enter the dimensions. Length, width, and thickness in any combination of feet, inches, or meters. The calculator converts internally.
- Choose units. Most US contractors use feet for length and inches for thickness — that combination is selectable directly.
- Add a waste allowance. 5–10% is standard. Anything under 3 yd³ also incurs a short-load fee, so round up generously.
- Read the cubic yards. The headline result is yd³. You also get cubic feet, cubic meters, and a bag count for bagged installs.
Formula
Cubic yards = (Length × Width × Thickness in feet) ÷ 27
Worked example
A 20 ft × 30 ft × 4 in slab equals 200 ft³ ÷ 27 = 7.4 cubic yards. Add 10% waste → order 8.1 yd³. No short-load fee at this volume.
Tips for accurate results
- A cubic yard is 27 cubic feet — the formula is L × W × T (in feet) ÷ 27.
- Ready-mix trucks deliver in 1-yard increments, with a 3-yard minimum to avoid the short-load fee.
- For thickness in inches, divide by 12 to convert to feet before multiplying.
- Round up the final order — a partial load can cost more than the wasted concrete.