Raised bed soil calculator
Enter each bed’s inside dimensions to see how much soil you need, how many bags that is, and how much of each ingredient to mix.
32.0 cu ft
- Cubic yards
- 1.19 (1.30 with extra)
- Litres
- 906 L (0.91 m³)
- Bags
- 22 (25 with extra)
- Screened topsoil
- 19.2 cu ft (60%)
- Compost
- 9.6 cu ft (30%)
- Perlite or pumice
- 3.2 cu ft (10%)
How the volume is calculated
Volume = length × width × depth. In inches, divide by 1,728 for cubic feet; divide cubic feet by 27 for cubic yards. Measure the inside of the frame. Loose soil settles by roughly 10–20% in the first season, so top up or buy a little extra.
Mel’s Mix is the blend from Mel Bartholomew’s All New Square Foot Gardening: equal parts compost, peat moss (many gardeners now use coir) and coarse vermiculite. It is light and drains well but costs more than a topsoil-based blend.
Planning what goes in the bed? Use the spacing calculator and the companion planting chart.
Questions gardeners ask
How much soil do I need for a 4×8 raised bed?
A 4×8 ft bed 12 inches deep holds 32 cubic feet, about 1.2 cubic yards or 906 litres. That is roughly 22 bags of 1.5 cu ft or 16 bags of 2 cu ft. Buy 10–15% extra because new soil settles.
Is it cheaper to buy soil in bulk?
Usually yes above about 1 cubic yard (27 cubic feet). Many garden centres and landscape yards deliver blended raised-bed mix by the yard.
Do I need to fill the whole bed with soil?
Most vegetables root in the top 12 inches. Deep beds can be part-filled with logs, branches and leaves underneath (hugelkultur style), topped with 10–12 inches of good mix, though that settles more.