Millimeter of Water (mm)
Water · Metric
Main conversion
1 mm = 10 m³/ha (1 L/m²)
Description and history
The millimeter of water (symbol mm) is the standard unit for rainfall and irrigation as water depth: 1 mm over 1 m² equals exactly 1 liter.
In agronomy it is the reference for evapotranspiration (ET₀, ETc), water balances and irrigation scheduling.
Reference conversions
| Unit | Equals |
|---|---|
| Centimeter of Water (cm) | 1 mm = 0.1 cm |
| Cubic Meter per Hectare (m³/ha) | 1 mm = 10 m³/ha |
| Liter per Square Meter (L/m²) | 1 mm = 1 L/m² |
| Liter per Hectare (L/ha) | 1 mm = 10,000 L/ha |
| Inch of Water (in) | 1 mm = 0.03937 in |