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Last updated: 3 October 2026
Potting mix calculator
Work out the potting mix to fill your containers. Australian units: metres, centimetres and litres. Results update as you type.
How to use this calculator
Count your pots and pick the pot size. Pot sizes are usually printed on the base or the label in litres.
Fill pots to just below the rim so there's room for watering.
How it's calculated
Total volume = number of pots × pot volume. Litres are divided by the bag size to give bags.
Worked example
10 pots of 10 litres each need 10 × 10 = 100 litres, which is 4 bags of 25 litres.
Common questions
Should I buy extra?
Potting mix settles after the first few waterings, so it's worth keeping a little spare to top up.
Can I reuse last year's potting mix?
You can refresh it by mixing in fresh mix or compost, but for seedlings and heavy feeders fresh mix usually gives better results.
Do I need drainage material?
Most plants need a pot with drainage holes. Check the needs of your plants.