Dew Point Calculator
Enter the air temperature and relative humidity to find the dew point. The tool shows the result in Celsius and Fahrenheit, explains what the number means with comfort bands, and shows the formula it uses.
Dew point
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°C
Dew point
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°F
Formula used
γ(T,RH) = ln(RH/100) + (17.625 × T) / (243.04 + T)
Dew point = 243.04 × γ / (17.625 − γ)
This is the Magnus formula (Sonntag coefficients b = 17.625, c = 243.04), with T in Celsius. Accurate for normal indoor and outdoor temperatures.
How to use
- Type the air temperature and pick Celsius or Fahrenheit.
- Type the relative humidity as a number from 1 to 100.
- Click Calculate to see the dew point and what it feels like.
Dew point vs humidity
Relative humidity is a percentage that changes as the temperature changes, so 60% can feel fine on a cool day and sticky on a hot day. Dew point is an absolute measure of how much moisture is in the air, so it is the better guide for how humid the air actually feels.
Frequently Asked Questions (FAQ)
What is dew point?
Dew point is the temperature at which air becomes fully saturated and water vapor starts condensing into liquid dew. Higher dew point means more moisture in the air.
How is dew point different from relative humidity?
Relative humidity is a percentage that changes with temperature, while dew point is an absolute measure of moisture. Dew point tells you how humid the air actually feels.
Which formula does this calculator use?
It uses the Magnus formula with the Sonntag coefficients b = 17.625 and c = 243.04, accurate for normal outdoor and indoor temperature ranges.
What dew point is considered comfortable?
Below 10 C feels dry and crisp, 10 to 16 C is comfortable, 16 to 18 C is slightly humid, 18 to 21 C feels muggy, and above 21 C feels oppressive.