The chart values are pure geometry. They do not include waste, thickened edges, excavation variation, minimum orders, or a recommendation about suitable thickness.
01 / Formula
How this is calculated
Cubic yards = length ft × width ft × thickness in ÷ 32402 / Assumptions
What the estimate assumes
- ✓Every footprint is rectangular.
- ✓Thickness is constant.
- ✓Values are rounded to two decimals and exclude waste.
03 / Worked example
See the math in context
For 12 × 20 ft at 4 inches: 12 × 20 × 4 ÷ 324 = 2.96 cubic yards.
04 / Guidance
Common reference values
10×10 ft: 1.23 yd³ at 4 in, 1.54 at 5 in, 1.85 at 6 in. 12×20 ft: 2.96, 3.70, 4.44. 20×20 ft: 4.94, 6.17, 7.41. 20×24 ft: 5.93, 7.41, 8.89.
05 / Guidance
Use the calculator for ordering
A chart is useful for a fast sense check. For purchasing, enter actual formed dimensions and a deliberate allowance in the slab calculator.
Questions
Frequently asked
Should I order exactly the calculated amount?+
Usually no. Excavation variation, form dimensions, spillage, and uneven subgrade can increase actual volume. Use the editable waste allowance and discuss minimum loads and order increments with the supplier.
How many cubic feet are in a cubic yard?+
There are exactly 27 cubic feet in one cubic yard. Divide cubic feet by 27 to convert to cubic yards.
Does this replace a structural design?+
No. These tools estimate material quantity only. A qualified professional and applicable plans, codes, site conditions, reinforcement requirements, and manufacturer instructions govern the project.
Sources