Raised Bed Soil Calculator

How it is calculated

All three measurements are entered in centimetres. The tool multiplies them to get the volume in cubic centimetres and converts to litres, because 1000 cm³ is 1 litre: litres = length × width × depth ÷ 1000. Cubic metres are litres ÷ 1000, shown with two decimals. The bag count assumes 50-litre bags and is always rounded up to a whole bag: bags = ⌈litres ÷ 50⌉.

All dimensions must be greater than zero. The depth is the depth of the soil you put in, not the height of the frame, and the bed is assumed to be a plain rectangle filled to the top, with no allowance for settling or for a layer of other material at the bottom. Only 50 L bags and metric units are used here. For other bag sizes, divide the litres by the size on your bag.

Common mistakes

• Entering metres or feet. The fields are centimetres, so a 2.4 m bed typed as 2.4 gives a volume 100,000 times too small.
• Using the height of the frame instead of the depth of soil. If the soil will sit 5 cm below the rim, enter the filled depth, not the board height.
• Not allowing for settling. Fresh compost-rich soil sinks after watering, so many gardeners buy a bag or two more than the tool shows.
• Buying exactly the litres figure with a different bag size. The bag count assumes 50 L bags; 40 L bags would need 22 for the same bed.
• Counting a bed that has a lower layer of branches, gravel or turf. Those fill part of the depth, so enter only the depth that will be soil.