Vapour pressure of water

The vapour pressure of water may be approximated by the following relations (in order of increasing accuracy):

• ${\displaystyle P=\exp \left(20.386-{\frac {5132\,\mathrm {K} }{T}}\right)\,\mathrm {mmHg} }$

  where P is the vapour pressure (mmHg) and T is the temperature in kelvin.