A little less garden maths
How much compost
do I need?
Measure your rectangular bed, choose the depth you want to add, and we’ll work out the volume and number of bags.
Start with your measurements.
A quick example.
A bed 2 metres long and 1 metre wide, with a 5 cm layer, needs 100 litres. That’s two 50-litre bags.
What if my bed is an unusual shape?
Split it into rectangles, calculate each section separately, then add the volumes together before dividing by the bag size. This calculator does not measure circles or sloping beds.
Can I use this for a whole raised bed?
Yes, for the volume of a rectangular space. The calculation does not choose a growing mix or tell you how deep your compost layer should be. Enter the depth you actually intend to fill.
What is the calculation?
Metric: length in metres × width in metres × depth in centimetres × 10 = litres. For feet and inches, one cubic foot equals 28.316846592 litres. Divide the volume by your bag size, then round up to a whole bag.
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