mg/kg
milligram per kilogram of dry air
Humidity ratioexact by definition
The milligram per kilogram of dry air is 10⁻⁶ kg/kg, which is one part per million by mass. It is the unit for desiccant-dried and compressed air, where the humidity ratio is far too small for the g/kg of a psychrometric chart: instrument air at a −40 °C dew point holds about 80 mg/kg.
| 1 mg/kg | 0.001 g/kg |
Solvers that use humidity ratio