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Dew Point Calculator

Calculates dew point given air temperature in ℃ and % relative humidity.

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Formula : (fcC=ln(fcRH/100)+17.67*fcT/(243.5+fcT))*0+(243.5*fcC/(17.67-fcC))

T ℃ (fcT) = The temperature ℃
RH% (fcRH) = The relative Humidity %

Example 1

Value Keystrokes Display Description
20 T ℃ 20.00 Stores the temperature.
50 RH% 50.00 Stores the RH %
  Tdp 9.270 Calculates the dew point.

Example 2

Using the values in example 1, calculate the RH% for a dew point of 68 and a temperature of 74.

Value Keystrokes Display Description
17 Tdp 17.00 Stores the dew point
  RH% 82.86 Solves for the RH%

This calculator uses the Magnus formula in the referenced Wikipedia article with the NOAA constants.

These valuations provide a maximum error of 0.1%, for

-30°C ≤ T ≤ +35°C;
1% < RH < 100%;

Reference:

Dew Point - Wikipedia