Raised bed soil calculator

How it works

The calculator multiplies length × width × fill depth, where the fill depth is the height of the bed minus the gap you leave below the rim for mulch and watering. Soil and compost settle, so it adds a margin (15% by default) to the amount you buy. It then converts the result to cubic feet, cubic yards, cubic metres, litres and common bag sizes.

Worked example

Worked example: a 4 × 8 ft bed made of two 2×6 boards is 11 in (0.917 ft) high. Filled to 1½ in (0.125 ft) below the rim the fill depth is 0.79 ft, so the net volume is 8 × 4 × 0.79 = 25.3 ft³, which is 0.94 yd³ or 0.72 m³. With 15% for settling, buy about 1.08 yd³ (0.82 m³), or 30 bags of 1 cu ft.

The results are estimates for planning and shopping. Check your measurements, and buy a little extra rather than too little.