Skip to content
Plantalya
Plantalya
Search
Encyclopedia
Tools Blog About
Language

Repotting calculator

Give me the diameter of the current pot. I give back the next size, the litres of mix it takes, and whether this is the season for it.

Free No account Runs in your browser

Current pot

Measure across the top, not the base.

Optional: a plant refines the step with its growth rate.

Season

Next pot

Diameter

—cm

Potting mix

—L

Signs it is time

  • Roots come out of the drainage hole, or coil on the surface.
  • The soil dries within a day or two, however much you water.
  • Water runs straight through without ever soaking in.
  • The plant has not grown in a full season and stays pale despite feeding.
  • The pot tips over on its own, or the root ball lifts out in one solid block.

How it works

The step is two to five centimetres, chosen from the current diameter and, if you pick a plant, from its growth rate: a fast grower gets one extra centimetre, a slow one gets one less. Small steps look timid, but a pot much too large is the classic way to rot a plant — the soil no roots have reached stays soaked for weeks. The volume treats the pot as a truncated cone whose base is three quarters of the rim and whose height is about its diameter, then removes fifteen per cent for the root ball you are moving over.

Other tools