cubic yard
Volumeexact by definition
The cubic yard is the volume of a cube one yard on a side, exactly 0.764554857984 m³, which is 27 cubic feet or about 765 litres. It is the standard unit for concrete, aggregate, topsoil and excavated material in North America. The factor is exact by definition.
Watch out: A cubic yard is 27 cubic feet, not 3. Cubing a linear factor of 3 is where most volume conversion errors in construction come from.
| 1 yd³ | 764.55486 L |
About the cubic yard
The cubic yard is the unit of anything delivered by truck. A standard ready-mix concrete truck carries 8 to 10 cubic yards, a residential dumpster is rated in cubic yards, and topsoil, gravel and mulch are all sold that way. The reason it stuck is scale: a cubic foot is too small to price a driveway and a cubic metre was never adopted in the American trades, so the yard's cube landed in exactly the right size band, roughly the volume of a domestic chest freezer.
The arithmetic trap is the factor of 27. A slab 20 ft by 30 ft at 4 in thick is \(20 \times 30 \times \tfrac{1}{3} = 200\) cubic feet, which is 7.4 cubic yards, so you order 8 and allow for waste. Anyone who divides by 3 instead of 27 orders nine times too much concrete. The metric equivalent is friendlier here, since a cubic metre is 1.31 cubic yards and the same slab is 5.7 m³, but North American suppliers price in yards and will quote in yards no matter what the drawing says.