Calculator for the Saturation Vapor Pressure
The saturation vapor pressure for water vapor is the pressure at which the water in the air is in a balanced state between solid, liquid and gaseous, i.e. the water neither evaporates nor condenses nor freezes. This is the upper limit for the pressure of the vapor on the air. It increases exponentially with temperature. The saturation vapor pressure can only be calculated for air over a surface of water or ice and this calculation is not very accurate either. Depending on the temperature, air that is over land is roughly comparable to that over water or ice..
Temperature range over water: −45°C to 60°C
Temperature range over ice: −65°C to 0.01°C
The calculation is made using the Magnus formula. This reads:
Over water: E = 6.112 hPa * e 17.62 * t / ( 243.12 + t )
Over ice: E = 6.112 hPa * e 22.46 * t / ( 272.62 + t )
E is the saturation vapor pressure in hectopascals or millibars, t is the temperature in degrees Celsius.