Raised bed soil calculator: how to fill it
Fill volume = inner length × inner width × fill height. A Brick Premium bed 1.8 × 0.9 m with a height of 54 cm holds 708 l right to the rim (0.71 m³).
- 708 l
- fill for a 1.8 × 0.9 m bed to the rim
- 60 mm
- wall thickness you subtract twice
- 1,000
- litres make one m³
Updated 13/10/2026
Why count the inner size
The bed's walls are 60 mm thick. So you subtract the wall thickness twice from both the outer length and width. Long beds have a divider in the middle that reduces the volume a bit further.
Fill volume for common sizes
| Bed size | Per 10 cm | Height 30 cm | Height 42 cm | Height 54 cm |
|---|---|---|---|---|
| 1.2 × 0.6 m | 52 l | 156 l | 218 l | 280 l |
| 1.2 × 0.9 m | 84 l | 253 l | 354 l | 455 l |
| 1.2 × 1.2 m | 117 l | 350 l | 490 l | 630 l |
| 1.8 × 0.6 m | 81 l | 242 l | 339 l | 435 l |
| 1.8 × 0.9 m | 131 l | 393 l | 550 l | 708 l |
| 1.8 × 1.2 m | 181 l | 544 l | 762 l | 980 l |
| 2.4 × 0.6 m | 109 l | 328 l | 460 l | 591 l |
| 2.4 × 0.9 m | 178 l | 534 l | 747 l | 960 l |
| 2.4 × 1.2 m | 246 l | 739 l | 1,034 l | 1,330 l |
| 3 × 0.6 m | 138 l | 415 l | 581 l | 746 l |
| 3 × 0.9 m | 225 l | 674 l | 943 l | 1,213 l |
| 3 × 1.2 m | 311 l | 933 l | 1,306 l | 1,680 l |
How to fill a raised bed by layer
A layered fill saves soil and the bottom layers gradually turn into nutrients. Order from the bottom:
- Coarse material: branches, wood chips. Holds its shape and water drains through it easily.
- Grass and leaves: turf turned roots-up, mown grass, leaves.
- Compost: partly rotted or finished, feeds plants for a few more seasons.
- Topsoil: good garden soil or compost the plants can root into.
Choose the layer thickness based on what you have in your garden. The calculator works out the litres for each layer.
The fill will settle
A layered fill settles in the first season as the coarse material breaks down. Keep some soil back to top it up. We don't sell soil or compost: buy it at a garden centre or builders' merchant, bagged or loose by the m³.
Frequently asked questions
How much soil does a raised bed need?
Multiply the inner length, width and fill height. A 1.8 × 0.9 m bed with a height of 54 cm holds 708 l to the rim.
Do I have to fill the bed right to the rim?
No. Leave a few centimetres below the rim so water doesn't overflow when you water it. You set that in the calculator.
What should go on the bottom of a raised bed?
Coarse material like branches and chips. If you get voles in the garden, lay mesh on the bottom before the first layer.
How many bags of soil should I buy?
Divide the volume by the bag size on the packaging and round up. The calculator does it for you.