Calculate Temperature, Dewpoint, or Relative Humidity


1) Choose a temperature scale.
2) Enter values in 2 of the 3 boxes.
3) Press "Calculate" to find the missing value.

Fahrenheit      Celsius

Temperature T (°)     

Dewpoint Td (°)     

Relative Humidity RH (%)     


* Values are calculated using the August-Roche-Magnus approximation.

* Equations for each unknown written in terms of the two knowns.

* Spreadsheet-ready equations for each unknown in terms of the two knowns:
    RH: =100*(EXP((17.625*TD)/(243.04+TD))/EXP((17.625*T)/(243.04+T)))
    TD: =243.04*(LN(RH/100)+((17.625*T)/(243.04+T)))/(17.625-LN(RH/100)-((17.625*T)/(243.04+T)))
     T: =243.04*(((17.625*TD)/(243.04+TD))-LN(RH/100))/(17.625+LN(RH/100)-((17.625*TD)/(243.04+TD)))
     (-- replace "T", "TD", and "RH" with your actual cell references)
     (-- T and TD inputs/outputs to the equations are in Celcius)

Created & Maintained by Brian McNoldy

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