Weather / Humidity
Dew Point Calculator
Find the dew point from air temperature and relative humidity, or the humidity from the dew point, in °C or °F, with how muggy that dew point feels.
Dew Point Calculator: The calculator uses the Magnus formula with Bolton's (1980) coefficients, the form the MetPy weather library uses, accurate to about 0.1 °C for everyday temperatures. At 30 °C and 70% humidity, the dew point is 23.9 °C; at 20 °C and 50%, it is 9.3 °C. Runs 100% locally in your browser with zero server file uploads.
- Category
- Everyday tools
- Runs
- In your browser
- Cost
- Free · no sign-up
- Availability
- Ready to use
Runs entirely in your browser
The dew point is the temperature at which the air would be saturated: surfaces colder than it collect condensation, and fog forms when the air cools to it. It shows how muggy it feels better than relative humidity, which changes with temperature.
Dew point and comfort
Sweat cools the body by evaporating, and it evaporates more slowly the more moisture the air holds, which the dew point measures directly. Below 10 °C the air feels dry; 16–18 °C feels slightly humid; above 24 °C feels oppressive and makes heat illness more likely.
For how hot it feels overall, combine temperature and humidity with the heat index calculator.
Condensation and mould at home
Indoors, condensation forms where a wall, window, or pipe is colder than the room's dew point. At 20 °C and 60% humidity the dew point is 12 °C, so a window colder than that will run with water; lowering the humidity to 45% brings the dew point down to about 8 °C.
How to use it
- Enter the air temperature and the relative humidity.
- Read the dew point and how comfortable it feels.
- Switch to the second mode to find the humidity from a dew point instead.
Privacy & limitations
Everything is worked out in your browser.
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Frequently asked questions
What dew point feels comfortable?
Below about 13 °C (55 °F) most people find the air comfortable; from 16 °C (60 °F) it starts to feel humid, and above 21 °C (70 °F) it feels oppressive, whatever the temperature.
Why use the dew point rather than relative humidity?
Relative humidity depends on the temperature: 50% feels dry on a cold morning and sticky on a hot afternoon. The dew point measures the actual moisture in the air, so it tracks how muggy it feels.
When does condensation form?
On any surface colder than the dew point, such as a cold drink, a window in winter, or a cold-water pipe; fog and dew form when the air itself cools to it.
Free tool · runs in your browser · no account required