Formula
Courses are the bed height divided by the sleeper face, rounded up.
Each course has two long sides and two short sides. A side longer than one sleeper takes whole sleepers first, then a cut piece.
Cut pieces are fitted into sleepers longest first, reusing an offcut whenever it is long enough. Sleepers are the whole ones plus the ones opened for cuts.
Worked example
400 mm of 200 mm sleepers is 2 courses. Each course is two sides of 2.4 m and two of 1.2 m.
On 2.4 m sleepers that is 4 used whole and 2 opened for cuts, reusing offcuts: 6 sleepers.
Assumptions
Sides are entered as outside sizes. With butt joints the short sides can be cut shorter by two sleeper thicknesses, which only leaves more offcut.
There are no joins inside a side shorter than one sleeper, and no saw allowance.
Corner posts, screws and liner are not counted. The Raised bed page works out the soil.
Checked
Checked 11 November 2026. Wickes lists a garden sleeper at 2400 × 200 × 100 mm. Bunnings lists treated pine sleepers at 200 × 75 mm and 200 × 50 mm, in 1.8 m, 2.4 m and 3.0 m lengths.