How this calculator works
This runs our topsoil calculator on the beds. The soil is the area of all the beds times their height, plus an allowance for settling, and a bag is a given number of litres. The frames use boards of 150 mm stacked to the height, with a post at each corner.
Worked example: two 2.4 × 1.2 m beds, 300 mm high, take 1.90 m³ of soil with 10% settling, which is 39 bags of 50 litres. The frames are 2 boards high and take 12 boards of 2.4 m with 8 corner posts, and 6.3 m² of membrane lines the bottoms.
Soil for one raised bed (300 mm high, 10% settling, 50 litre bags)
Boards of 150 mm, 2.4 m long.
| Bed | Soil | Bags | Boards |
|---|---|---|---|
| 1.2 × 1.2 m | 0.48 m³ | 10 | 4 |
| 2.4 × 1.2 m | 0.95 m³ | 20 | 6 |
| 3 × 1.2 m | 1.19 m³ | 24 | 7 |
| 3.6 × 1.2 m | 1.43 m³ | 29 | 8 |
Tips before you buy
- Fill the bottom of a deep bed with cheaper material such as logs or compost, topped with good soil.
- Position beds where they get at least six hours of sun, with water close by.
- Line the bottom with cardboard or membrane to stop perennial weeds, but leave drainage.
- Make the paths wide enough for a wheelbarrow.
- Buy soil in bulk if you can: it is far cheaper than bags.
Tools & materials for this project
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Frequently asked questions
How much soil do I need for a 2.4m x 1.2m raised bed?
0.95 m³ at 300 mm deep with 10% extra, which is 20 bags of 50 litres. Two beds need 1.90 m³.
How many boards for a raised bed?
6 boards of 2.4 m make one bed 2 boards high (150 mm each): two long sides and two ends.
How deep should a raised bed be?
150 to 300 mm is enough for most vegetables, and deeper beds suit root crops or a bed on poor ground.
Is bulk soil cheaper than bags?
Yes, by a large margin once you need more than about half a cubic metre. Compare the price per m³ and the delivery charge.
Add this calculator to your website
Running a blog, a contractor site or a class page? You can put this calculator on it for free. Copy the code below, and please leave the link underneath the calculator in place. The small script just resizes the frame to fit the results; if your site strips scripts, the calculator still works inside a scrolling frame.
Related calculators & guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.