Raised Bed Soil Calculator

Work out how many litres of compost or topsoil you need to fill a raised bed, and roughly how many bags that is.

How it works

The volume of a rectangular bed is its length times width times depth. Working in centimetres gives cubic centimetres, and there are 1,000 cubic centimetres in a litre:

Litres = ( length cm × width cm × depth cm ) ÷ 1000

The tool then divides the litres by your bag size to estimate bags. For a new bed, a mix of about two-thirds multipurpose or topsoil to one-third garden compost or well-rotted manure works well; buy a little extra as the fill settles.

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This tool is a planning aid and simply does the maths from the numbers you enter. Order a little extra to allow for settling. Page updated 19 Sep 2026.