Enter your air temperature and relative humidity to calculate the dew point temperature — the point at which air becomes saturated and moisture begins to condense. Choose your preferred unit system (°C, °F, or Kelvin) and get back the dew point, absolute humidity, and a comfort level indicator based on current conditions.
Dew Point Temperature
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Absolute Humidity
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Temperature-Dew Point Spread
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Comfort Level
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The dew point is the temperature at which air must be cooled (at constant pressure and humidity) for water vapor to condense into liquid water — forming dew, frost, or fog. When the air temperature drops to the dew point, the air is fully saturated and relative humidity reaches 100%.
Relative humidity (RH) is the percentage of water vapor in the air relative to the maximum amount the air can hold at that temperature. The closer the dew point is to the actual air temperature, the higher the relative humidity. When they are equal, RH is 100% and condensation occurs.
This calculator uses the Magnus formula: γ(T, RH) = ln(RH/100) + (b·T)/(c+T), then Tdew = c·γ / (b−γ), where b ≈ 17.625 and c ≈ 243.04°C. This approximation is accurate for temperatures between −40°C and 60°C and relative humidity above 1%.
Absolute humidity is the actual mass of water vapor present in a unit volume of air, typically expressed in grams per cubic meter (g/m³). Unlike relative humidity, it does not depend on temperature — it simply measures how much moisture is in the air in absolute terms.
A dew point below 10°C (50°F) feels dry and comfortable. Between 10–16°C it is pleasant. From 16–21°C it becomes noticeably humid. Above 21°C (70°F) feels oppressive and muggy, and above 24°C is considered extremely uncomfortable or dangerous for outdoor activity.
The dew point applies when temperatures are above 0°C, where water condenses as liquid dew. The frost point applies below 0°C, where water vapor deposits directly as ice (frost) without becoming liquid first. The frost point is slightly higher in temperature than the dew point under the same conditions.
No — the dew point can never exceed the actual air temperature. When the dew point equals the air temperature, relative humidity is exactly 100% and the air is fully saturated. Any further cooling causes condensation.
At higher altitudes, atmospheric pressure is lower, which affects how much water vapor air can hold. Air that rises and cools will reach its dew point at a certain altitude — this is the lifting condensation level, and it is where clouds typically form.