How to calculate air temperature from dew point and relative humidity
This inverse calculation starts with the vapor pressure represented by dew point. Dividing by relative humidity gives the required saturation vapor pressure, which the Magnus equation converts into an estimated air temperature.
The result is the air temperature consistent with both supplied values. It is not a forecast and does not account for changing pressure, sunlight, terrain, or airflow.
es(T) = es(Td) / (RH / 100); T = f⁻¹(es)How to use dew point and humidity to calculate air temperature
Enter the known dew point, select its temperature unit, and enter relative humidity as a percentage from more than 0 through 100. The calculator solves the inverse Magnus relationship and displays the reconstructed dry-bulb temperature in Celsius, Fahrenheit, and Kelvin.
Use values recorded for the same air sample. A dew point from one time or location and an RH reading from another can still produce a number, but that result may not describe a real observation.
- At 100% RH, the calculated air temperature equals the dew point.
- At less than 100% RH, the calculated air temperature is above the dew point.
- Humidity entered as 50 means 50%, not 0.50.
- The result is dry-bulb air temperature, not wet-bulb or surface temperature.
Air temperature example from a 10°C dew point and 50% humidity
A dew point of 10°C with 50% relative humidity corresponds to an estimated air temperature of about 20.8°C, or 69.4°F. Substituting that temperature and the original dew point into the RH formula returns approximately 50%, providing a useful reverse check.
Small differences can appear when source readings are rounded or another Magnus coefficient set is used. Keep more decimal places for technical comparisons, but do not interpret calculator precision as instrument accuracy.
When an air temperature from dew point and RH calculator is useful
The inverse tool is useful for checking weather observations, environmental-monitoring records, and classroom examples where dew point and relative humidity are known but dry-bulb temperature is missing.
Calculated values should be treated as estimates. Sensor precision and rounding can make a reconstructed temperature differ slightly from the original reading.
Why calculated air temperature is not a weather forecast
The equation reconstructs one temperature that is mathematically consistent with the supplied dew point and relative humidity. It does not predict how temperature will change, whether moisture will enter or leave the air, or how sunlight, wind, terrain, and pressure will evolve.
For observation quality control, compare the result with sensor tolerances and the time stamps of the original readings. For forecasts or safety decisions, use current information from an official meteorological service.
Air temperature calculator questions for humidity observations
Will the calculated temperature always be above dew point?
Yes for valid relative humidity values of 100% or less. At exactly 100%, the calculated air temperature equals dew point.
Does this calculate wet-bulb temperature?
No. Wet-bulb temperature is a different quantity and can require pressure and psychrometric relationships not used here.
Why can the result differ by a few tenths?
Displayed observations are often rounded, and different vapor-pressure approximations use slightly different constants.