Cubic yards to cubic feet (cu yd to cu ft)

One cubic yard is exactly 27 cubic feet. That ratio belongs to the customary system itself and is much older than any link to metric: the 1959 international yard and pound agreement later fixed the yard and the pound against the meter and the kilogram, but it left the ratios between customary units (feet to the yard, ounces to the pound, cups to the gallon) exactly as they were.

Worked through: 3 cu yd x 27 = 81 cu ft.

Going the other way, one cubic foot is 0.037037037 cubic yards.

For mental arithmetic: Multiply by 27: multiply by 30 and take off a tenth.

Twenty-seven, because a yard is three feet and volume cubes the length factor: three cubed. That squaring and cubing of a linear factor is the thing most often got wrong in takeoff: a cubic yard is 27 cubic feet, not 3, and a square yard is 9 square feet, not 3. The practical use is ordering: concrete, gravel, mulch and topsoil are sold by the cubic yard in the US and measured on site in feet, so every materials estimate crosses this factor exactly once.

Precision is worth matching to the input. A measurement given as 0.5 cu yd carries one or two significant figures, and reporting its conversion to six implies a precision the original never had.