Dew Point Calculator
Dew point from temperature and humidity — the honest humidity gauge.
The Dew Point Calculator derives the dew point from air temperature and relative humidity using the Magnus formula. The dew point — the temperature at which air saturates and moisture condenses — is the most honest single number for how humid it actually feels.
Relative humidity is misleading alone: 90% humidity at 10 °C feels dry-ish, while 50% at 32 °C feels muggy, because what your skin feels is the dew point. Below about 13 °C dew point air feels comfortable; above 18 °C it turns sticky, and 24 °C+ is oppressive — the scale most meteorologists actually use.
The same number explains morning dew on grass, fog formation and when your glasses fog up. The calculation is exact and runs locally in your browser, in °C or °F.
Dew point
13.9 °C
≈ 56.9 °F
Comfort reading
Comfortable
dew point scale
The dew point is the temperature at which air saturates and moisture condenses — computed here with the Magnus formula. It is a better humidity gauge than relative humidity alone: dew points above 18 °C feel sticky, below 10 °C feel dry.
How to use the Dew Point Calculator
- Enter the air temperature.
- Enter the relative humidity in percent.
- Choose °C or °F.
- Read the dew point and its comfort reading.
- Compare cities or days — the dew point is the honest comparator.
Frequently asked questions
How is the dew point calculated?
Using the Magnus formula: dew point = c·γ ÷ (b − γ), where γ = ln(RH/100) + b·T/(c+T), with b = 17.62 and c = 243.12 for °C. It is accurate to well within a degree across normal ranges.
Why is the dew point better than relative humidity?
Relative humidity changes with temperature, so a cool morning and a warm afternoon report very different numbers for the same actual moisture. Dew point is absolute — it tells you directly how much water is in the air and how it will feel.
What happens when temperature meets the dew point?
The air saturates: dew forms on surfaces, fog can develop, and your glasses fog when they are colder than the dew point. That is why a rising dew point through the day often signals rain coming.
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