Raised Bed Soil Calculator
Enter the size and number of beds and your soil mix. You get the volume, the bags and the split between topsoil, compost and sand, plus the timber for the sides.
This is an estimate. Soil settles in the first year, so top the beds up each spring.
Worked examples
Two vegetable beds
Each 2.4 m by 1.2 m by 0.3 m, half topsoil and half compost, 10% settling
1.9 cubic metres, 39 bags of 50 litres
That is 0.95 cubic metres of topsoil and 0.95 of compost. Timber for one layer of board round the beds is 14.4 m.
About Raised Bed Soil Calculator
A raised bed calculator tells you how much soil and compost to buy to fill one bed or several. The volume is the length times the width times the depth of the bed, then increased by a little because the soil settles in the first weeks. Enter the size and the number of beds, and the mix you want as parts of topsoil, compost and sharp sand, and you get the volume of each and the number of bags.
If you plan to put logs or rough prunings in the bottom of a deep bed, enter the share of the depth they will fill and you will need less soil. The tool also works out the length of timber for the sides, from the distance around each bed and the number of boards that stack to the height you want. Corner posts and fixings are extra.
How to use Raised Bed Soil Calculator
- Enter the length, width and depth of one bed and the number of beds.
- Set the mix as parts of topsoil, compost and sand.
- Enter any bulky fill, the extra for settling and your bag size.
- Read the volume, bags and timber.
Common uses
- Building vegetable beds
- Filling planters
- Comparing bagged and bulk deliveries
- Planning a raised herb garden
Frequently asked questions
How much soil do I need for a raised bed?
Multiply length by width by depth. A bed 2.4 m by 1.2 m and 0.3 m deep holds 0.864 cubic metres. For two beds with 10% for settling that is 1.9 cubic metres, or 39 bags of 50 litres.
What should I fill a raised bed with?
A common mix is half topsoil and half well rotted compost or manure. Some gardeners add up to a tenth of sharp sand for drainage, and a filling of logs in the bottom of deep beds.
How deep should a raised bed be?
Thirty centimetres is enough for most vegetables. Root crops such as parsnips and carrots do better at 45 cm or more.
How wide should a raised bed be?
No more than 1.2 m, so that you can reach the middle from either side without stepping on the soil.
Why does the soil need topping up?
Fresh soil and compost settle and break down in the first year. An extra 10% is included, and many people top up each spring.