Plant pot size calculator
Tell us the pot your plant is in now and where it lives. We will tell you the size to buy next, and show you the pots that fit.
What size plant pot do I need?
Measure the diameter across the top of the pot your plant is in now, then add 3 to 5cm. A 12cm pot moves up to 15 or 17cm, not 25cm. Going up gradually matters, because spare compost holds water the roots cannot reach, and that stagnant water is what rots them.
- Measure the top diameter of the current pot, rim to rim
- Add 3 to 5cm for a repot, or 1 to 2cm for a cover pot
- Never jump several sizes - wet compost rots roots
- Repot in spring, once roots circle the base
Buy a pot 15 to 17cm across the top.
By size
Shop the size you landed on
Every band below is sized on the top diameter, the same measurement the calculator uses.
Questions
Pot sizing - FAQs
How do I measure a plant pot?
Measure straight across the top of the pot, rim to rim, in centimetres. Pot sizes are always quoted as that top diameter, not the height and not the base.
What if my plant is in a plastic nursery pot?
Measure the nursery pot. If you want a decorative cover pot rather than repotting, add only 1 to 2cm so the nursery pot sits neatly inside it.
Can I skip a size and save myself a repot?
It rarely works. A much larger pot holds compost the roots cannot dry out, so it stays wet for weeks and the roots rot. One size at a time is faster in the end.
Does pot depth matter as well as width?
For most houseplants width is the number that matters. Depth matters for potatoes, tomatoes and anything with a taproot, and for trees, where depth gives stability.
When is the best time to repot?
Spring or early summer, while the plant is growing actively and can recover quickly. Avoid repotting in the depths of winter when growth has slowed right down.
How do I know the plant needs repotting at all?
Roots circling the base, roots poking out of the drainage holes, water running straight through, or growth that has stalled in the growing season. Any of those means it is time.