Cubic metres, cubic yards and cubic feet: a practical conversion

Length conversion factors must be cubed when converting volume. One yard is three feet, so one cubic yard contains 27 cubic feet. Treating it as three cubic feet produces a ninefold error.

A worked example

Item	Example or check
1 ft	0.3048 m
1 ft³	0.028316846592 m³
1 yd³	0.764554857984 m³
2 m³	About 2.6159 yd³

Check the assumptions

Keep full precision during the calculation and round the displayed result at the end. Supplier order increments may be much coarser than the mathematical conversion. Record both the exact target and the rounded order so a later reviewer can see why they differ.

For a 10 ft × 10 ft slab with a 4 in depth, convert depth to 4/12 ft. The volume is 33⅓ ft³, or about 1.23457 yd³ before any extra allowance. Converting the dimensions to metres first must lead to the same physical result.

Before using the estimate

Square feet measure area. Cubic feet measure volume. A floor area alone cannot determine concrete or gravel volume without a depth.

Open the Concrete Calculator and compare your measurements with the example.