Raised Bed Materials Calculator

Measure bed dimensions

Soil volume uses filled length × width × depth. If measurements are external and boards are thick, change them to internal dimensions first.

Measure the internal length and width that soil actually occupies. If measuring outside the frame, subtract board thickness on both sides before estimating soil. Use the filled soil depth; it can be lower than frame height to leave watering space. The bed count assumes equal beds. Calculate differing beds separately, then combine the soil bags to be bought.

Count board courses

Divide soil depth in millimetres by board face width and round up. One course per bed has two long and two short cuts.

A 150 mm board face and 300 mm height require two courses. The estimate packs longer cuts first, then reuses offcuts after subtracting the entered saw-cut width. The 3 mm default is illustrative; confirm the actual blade or cutting service before ordering. Corner-joint geometry and board thickness still need separate checks.

Reuse cuts

Two default beds need eight 2 m cuts and eight 1 m cuts. With a 3 mm saw cut, a 3 m board cannot yield a 2 m and a 1 m piece together: eight boards serve the long pieces and four more serve paired short pieces, or 12 boards. Deliberately entering a zero cut width restores the eight-board exact fit. Soil is 0.6 m³ per bed, 1.2 m³ for two, or 1.26 m³ with allowance: 32 bags of 40 L.

Order soil

Base soil is 1.2 m³; with 5% allowance it is 1,260 L or 32 bags of 40 L. The cut plan includes the entered saw cut but omits corner posts and bracing; check your assembly.

The board total omits corner posts, bracing, fixings, barriers and any base fill. Soil pressure and moisture affect the frame, especially long sides, so choose materials and assembly for the site. For bulk soil instead of bags, use the order volume of 1.26 m³ as a starting enquiry and confirm whether the supplier quotes loose or placed volume.