Work out plant watering amount instantly with clear inputs, formula shown and shareable results.
Soil volume is the pot's cross section times the soil depth, and a thorough watering delivers about a fifth of that volume so water reaches the base without flooding. Watering by volume rather than by eye is what prevents the shallow surface wetting that leaves roots dry and encourages fungus gnats.
Soil volume
volume = pi x (diameter / 2)^2 x soil depth
Water per watering
water ml = soil volume x water share
volume = pi x (diameter / 2)^2 x soil depth. Soil volume is the pot's cross section times the soil depth, and a thorough watering delivers about a fifth of that volume so water reaches the base without flooding.
Watering by volume rather than by eye is what prevents the shallow surface wetting that leaves roots dry and encourages fungus gnats.
Enter pot diameter, soil depth, water as a share of soil volume, days between waterings. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.