Use actual formed diameter and thickness for round hot-tub pads, equipment pads, footings and other simple circular pours.
01 / Formula
How this is calculated
Cubic yards = π × (diameter ÷ 2)² × (thickness in ÷ 12) ÷ 27 × (1 + allowance %)02 / Assumptions
What the estimate assumes
- ✓The footprint is a true circle.
- ✓Thickness is uniform.
- ✓Reinforcement and structural suitability are outside the quantity calculation.
03 / Worked example
See the math in context
A 12-ft circle at 4 inches thick contains about 37.7 cubic feet, or 1.40 cubic yards before allowance.
04 / Guidance
Measure the formed diameter
Check more than one direction across the circle. If the excavation is irregular, use a justified allowance rather than rounding the diameter silently.
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