Dew Point Calculator

Dew point is calculated from air temperature and relative humidity using the Magnus-Tetens formula: first compute γ = ln(RH/100) + (17.27 × T)/(237.7 + T), then Td = (237.7 × γ)/(17.27 − γ). This calculator applies the formula instantly as you type, accurate to about 0.35 °C between −40 °C and +50 °C.

For indoor comfort, aim for a dew point between about 7 °C and 16 °C, which corresponds to 30–60% relative humidity at typical room temperatures. Below a 7 °C dew point the air feels dry (increasing static and dry skin); above 16 °C it feels humid and condensation risk on cold surfaces rises.

Relative humidity depends on temperature: the same moist air shows 50% RH at 20 °C but only 25% RH at 30 °C. Dew point measures the actual moisture content, so it stays constant as temperature changes. That is why dew point is the standard way to compare humidity across different times and places.

Most people notice mugginess once the dew point exceeds 18–20 °C. A dew point above 24 °C feels oppressive and can be dangerous during physical activity, because sweat evaporates poorly. Below 10 °C the air feels crisp and dry regardless of the relative humidity reading.

Yes — this page accepts air temperature plus either relative humidity or dew point. If you only have a wet-bulb reading, convert it first: e ≈ e_w − 0.00066 × (1 + 0.00115 × Tw) × P × (T − Tw), where e_w is saturation vapor pressure at the wet-bulb temperature. Then RH = 100 × e / es and enter the result here.