Relative Humidity Calculator
Enter the air temperature and the dew point to get therelative humidity — the percentage of moisture the air is holding versus the most it could hold at that temperature.
Evidence-checked. Facts and figures on this page are verified against published standards and government sources (Magnus dew-point formula (Sonntag coefficients)). Last verified July 2026 — our methodology.
Relative humidity
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- Absolute humidity
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- Dew point
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- How it feels
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Relative humidity is the ratio of the saturation vapor pressure at the dew point to the saturation vapor pressure at the air temperature, using the Magnus formula with Sonntag coefficients. The dew point can never be higher than the air temperature — at that point the air is fully saturated at 100%.
Temperature, dew point, and relative humidity
Relative humidity depends on two things: how much moisture is in the air (which the dew point measures) and how warm the air is. Warm air can hold far more water, so the same dew point gives a low RH on a hot afternoon and a high RH on a cool night. If you know your dew point from a weather app, this tool converts it to the percentage most thermostats and hygrometers display. To go the other direction — from humidity to dew point — use thedew point calculator, and to learn why dew point is the better mugginess gauge, readdew point vs relative humidity. For what counts as healthy indoors, seeideal indoor humidity levels.