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Plant Watering Amount Calculator

Work out plant watering amount instantly with clear inputs, formula shown and shareable results.

About Plant Watering Amount Calculator

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.

Formulas

Soil volume

volume = pi x (diameter / 2)^2 x soil depth

Water per watering

water ml = soil volume x water share

Worked example

With the default values below, Plant Watering Amount Calculator returns Water per watering of 1,131.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Pot diameterminimum 1 cm
20 cm
Soil depthminimum 1 cm
18 cm
Water as a share of soil volumeaccepts 1–60 %
20 %
Days between wateringsminimum 0.5
7

Results

Water per watering
1,131.0 ml
Soil volume in the pot
5,654.9 cm3
Average water per day
161.57 ml
Water used per month
4.847 L

Step by step

  1. 1Values used
  2. 2Soil volume
  3. 3Water per watering
  4. 4Water per watering= 1,131.0 ml
  5. 5Soil volume in the pot= 5,654.9 cm3
  6. 6Average water per day= 161.57 ml
  7. 7Water used per month= 4.847 L

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Plant Watering Amount figure worked out?

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.

Why does this matter?

Watering by volume rather than by eye is what prevents the shallow surface wetting that leaves roots dry and encourages fungus gnats.

What do I need to enter?

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.

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