Dew point and humidity
Dew point, vapour pressure and absolute humidity from a temperature and relative humidity, using the Magnus formula.
- Dew point
- Relative humidity
- Vapour pressure
- Absolute humidity
Dew point
Dew point13.221 °C≈55.8 °F
Spread6.779 °C≈how far the air must cool before it saturates; a small spread means fog or cloud is close
ComfortNoticeably humida conventional banding of how humid air feels, not a measurement
Vapour
Saturation vapour pressure23.3344 hPa≈
Actual vapour pressure15.1674 hPa≈
Absolute humidity11.2108 g/m³≈
Relative humidity65%
The formula used
FormulaMagnus, Alduchov and Eskridge (1996) coefficientsa = 17.625, b = 243.04 °C; other published coefficient sets differ in the third decimal place
NatureAn empirical fit, not physicssaturation vapour pressure has no closed-form expression, so every dew point figure comes from a curve fitted to measurements
Valid rangeAbout −40 °C to +50 °Coutside this the fit degrades