Container & Pot Compost Calculator

Estimate the litres of compost to fill round pots or containers of a given size, and how many bags you will need.

How it works

A round pot is treated as a cylinder, so its volume is pi times the radius squared times the depth. Dividing by 1,000 converts cubic centimetres to litres:

Litres per pot = π × (diameter ÷ 2)² × depth ÷ 1000

Real pots taper slightly, so this is a small overestimate, which is handy as compost settles. Leave a couple of centimetres at the rim for watering. Use peat-free multipurpose compost, or John Innes for long-term and permanent plantings.

Related calculators

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.