Cubic Yard Calculator
Volume of slabs, holes, footings and cylinders in cubic yards, feet and metres, several pieces added, with the depth in inches.
Volume of slabs, holes, footings and cylinders in cubic yards, cubic feet and cubic metres — several pieces added together, with the depth in inches because that is how it is measured.
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Twenty-seven cubic feet to the yard, and the depth is in inches. Slabs are 4 inches, footings 12, mulch 3; nobody measures those in feet, so the depth field takes inches and divides by twelve before it multiplies. A 20 × 12 slab at 4 inches is 80 cubic feet, 2.96 yards. Forgetting the twelve gives 960 cubic feet and a very surprised concrete plant.
Volume, not material. This is the geometry only. Concrete wants a waste factor, gravel a compaction allowance, excavated soil a swell factor, and each of those has its own page here that starts from this volume. Use this page when the question is simply how big the hole, the slab or the pile is.
Cylinders are footings and sonotubes. A 3-foot diameter pier 4 feet deep is 28.3 cubic feet, about a yard; twelve of them are twelve yards, which is a truck. The diameter is in feet here because piers are specified that way; a 12-inch sonotube is 1 foot.
Rectangular volume = length × width × depth ÷ 12; cylinder = π (d ÷ 2)² × depth. 1 yd³ = 27 ft³; 1 ft³ = 0.028316846592 m³ (exact).
Worked example
A 20 × 12 ft slab at 4 inches plus a 3 ft pier 4 ft deep: how many cubic yards?
- Slab: 20 × 12 × 4 ÷ 12 = 80 ft³.
- Pier: π × 1.5² × 4 = 28.27 ft³.
- 108.27 ft³ ÷ 27 = 4.01 yd³ (3.07 m³).
About 4 cubic yards of geometry — the concrete page adds the waste allowance on top of this figure.
5 values on this page were driven in a browser and compared with independently derived figures on 2026-09-05 (418 values across 51 calculators site-wide).
Questions
How many cubic feet in a cubic yard?
27. A 20 × 12 ft slab 4 inches thick is 80 ft³, so 2.96 yd³.
How do you calculate cubic yards from inches?
Length × width in feet × depth in inches ÷ 12 gives cubic feet; divide by 27 for yards. The page takes depth in inches so the ÷ 12 cannot be forgotten.