Cubic Yards Calculator
Result
Volume in cubic yards
- Volume
- 66.7 ft³
- Volume in cubic metres
- 1.89 m³
A cubic yard is 27 cubic feet, and it is the unit a ready-mix supplier quotes in. This calculator takes the three numbers you actually measure on site — length in feet, width in feet and slab thickness in inches — and gives the volume back three ways: cubic yards for the order, cubic feet to check the arithmetic, and cubic metres for a metric supplier. It assumes no material at all: a cubic yard of concrete, of gravel and of excavated spoil is the same cubic yard.
Cubic yards in cubic feet and cubic metres
| Cubic yards | Cubic feet | Cubic metres |
|---|---|---|
| 1 | 27 | 0.76 |
| 5 | 135 | 3.82 |
| 10 | 270 | 7.65 |
| 20 | 540 | 15.29 |
| 50 | 1350 | 38.23 |
One cubic yard is 27 cubic feet and 0.7646 cubic metres. A ready-mix truck carries 8 to 10 cubic yards, so the top two rows are a full load.
Formula
Volume (yd³) = length (ft) × width (ft) × thickness (in) ÷ 12 ÷ 27
- L
- Length of the area, in feet
- W
- Width of the area, in feet
- T
- Slab thickness or layer depth, in inches
Use it for a rectangular pour or a rectangular hole: a slab, a footing, a patio, a driveway, a trench backfill. An L-shaped area is split into rectangles, each run separately, and the volumes added. A round pour — a pier, a column base — is π × radius² × depth, which is a different page.
Worked examples
A 20 ft by 10 ft slab, four inches thick
- Area: 20 × 10 = 200 square feet
- Thickness in feet: 4 ÷ 12 = 0.333 ft
- Volume: 200 × 0.333 = 66.7 cubic feet
- Cubic yards: 66.7 ÷ 27 = 2.47 yd³
- Cubic metres: 66.7 × 0.0283168 = 1.89 m³
A ready-mix truck carries 8 to 10 cubic yards, so this is a quarter of a load. Ask the supplier whether a small load is cheaper than 34 bags mixed on site.
A 12 ft by 8 ft patio, six inches thick
- Area: 12 × 8 = 96 square feet
- Thickness in feet: 6 ÷ 12 = 0.5 ft
- Volume: 96 × 0.5 = 48 cubic feet
- Cubic yards: 48 ÷ 27 = 1.78 yd³
- Cubic metres: 48 × 0.0283168 = 1.36 m³
Thickness is the input worth measuring twice: the same patio at three inches is 0.89 cubic yards, and at eight inches it is 2.37.
Limitations
The shape is a rectangular box. A thickened edge, a footing under the slab, steps, a curb and a subgrade that is not flat all change the number — a slab two inches thicker at one end is not this box. Earthwork also has two volumes: undisturbed ground is measured in bank cubic yards and the same soil after digging in loose cubic yards, and spoil bulks up by 20% to 40% when it comes out of the hole, so a 2.47 cubic yard excavation is not 2.47 cubic yards of truck. Order concrete with a little to spare rather than exactly at the calculated figure.
Frequently asked questions
- How do I work out cubic yards by hand?
- Multiply length by width by thickness, all three in feet, then divide by 27. A 20 ft by 10 ft slab four inches thick is 20 × 10 × 0.333 = 66.7 cubic feet, and 66.7 ÷ 27 = 2.47 cubic yards. That division is the whole of the cubic yard conversion: 27 is simply how many cubic feet fit in a cubic yard.
- Why is slab thickness entered in inches rather than feet?
- Because that is how a slab is specified — a four-inch slab, a six-inch slab. Thicknesses under a foot are spoken in inches at every job site, and typing 0.333 to mean four inches is an invitation to a decimal error. The calculator does the division by 12 for you.
- How much does a cubic yard of concrete weigh?
- About 4,050 pounds, or 1.84 tonnes — normal-weight concrete runs around 2,400 kilograms per cubic metre. This page deliberately does not convert volume to weight, because the same 2.47 cubic yards is about 5 tons of concrete and about 1.4 tons of dry gravel.
- How many cubic feet are in a cubic yard?
- 27, because a yard is 3 feet and 3 × 3 × 3 = 27. It is the most useful number on this page: divide cubic feet by 27 to get cubic yards, multiply cubic yards by 27 to go back. One cubic yard is also 0.7646 cubic metres.
- Can the calculator handle an L-shaped slab?
- Not as one shape — split it into rectangles, run each one and add the cubic yards. Volume adds but average depth does not, so never average the two thicknesses and run the total area. A slab with a thickened edge is handled the same way: the slab and the thickened strip separately.
- How much extra should I order?
- Five to ten percent, rounded up to whatever increment the supplier sells in. Concrete cannot be topped up once it starts to set, and a pour that comes up short leaves a cold joint — the one defect that is cheaper to avoid than to repair. For 2.47 cubic yards, order 2.75 or 3.
References
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811 — Appendix B gives the exact factors used here, including 1 yd³ = 0.764 554 857 984 m³ and 1 ft³ = 0.028 316 846 592 m³ — National Institute of Standards and Technology
- Approximate Conversions from U.S. Customary Measures to Metric — the working chart for feet, inches, cubic feet and cubic yards — National Institute of Standards and Technology