Choose the target for your own plants and soil; this tool does not prescribe a watering schedule.
- One millimetre over one square metre equals one litre. Only effective rainfall counts; application efficiency is an explicit assumption.
Garden calculator
Watering Volume Calculator
Translate an entered water-depth target into volume after rainfall and application losses.
Method and practical checks
- One millimetre over one square metre equals one litre. Only effective rainfall counts; application efficiency is an explicit assumption.
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Worked example
Applying 20 mm of water to 20 m² needs 20 × 20 = 400 L, because 1 mm over 1 m² is 1 litre. A 200 L water butt would need filling 2 times.
| Input | Value |
|---|---|
| Measured sections | Length 5 m, Width 4 m |
| Target water depth | 20 mm |
| Effective rainfall | 0 mm |
| Application efficiency | 100 % |
| Storage capacity | 200 L |
| Result | Value |
|---|---|
| Net water needed | 400 L |
| Water to apply | 400 L |
| Full storage fills | 2 |
| Storage left after application | 0 L |
Reading the result
- Choose the target depth for your plants and soil; this tool converts it to litres rather than setting a watering schedule.
- Only rain that soaked in counts; subtract it before watering.
- Sprinklers and hoses lose water to evaporation and run-off; lower the efficiency to account for that.