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Dew Point Calculator

Dew point, humidity or temperature from the other two.

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Comfort scale

Dew point chart

Dew point

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Derived values

Absolute humidity—
Vapour pressure—
Saturation pressure—
Wet bulb (approx.)—

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Surfaces below this will collect water

Dew point is an absolute measure of moisture, which is why meteorologists prefer it: 80 percent humidity at 5 °C is dry air, while 80 percent at 30 °C is oppressive. Any surface colder than the dew point will collect water, which is why windows fog and cold drinks bead.

Quick Tool Overview

The Dew Point Calculator uses the Magnus-Tetens approximation to find dew point, relative humidity or air temperature from the other two, and reports absolute humidity, vapour pressure and wet bulb temperature alongside.

What it does
Solves dew point, humidity or temperature
You give it
Any two of the three
You get back
The third, plus absolute humidity and wet bulb
Best for
Weather, HVAC, condensation risk and comfort
Calculators Free, unlimited use No sign-up Runs in your browser

About the Dew Point Calculator

Calculate dew point from temperature and relative humidity, or solve for either of the others, using the Magnus-Tetens approximation. Absolute humidity, vapour pressure and the wet bulb temperature are reported alongside.

Dew point is the temperature air must cool to before water begins to condense out of it, and it is a far better guide to how humid the air actually feels than relative humidity is. Relative humidity is a percentage of a moving target, since warm air holds more moisture — 80 percent at 5 °C is dry air, while 80 percent at 30 °C is oppressive. Dew point is absolute, which is why meteorologists use it, and why it predicts condensation on cold surfaces so directly.

Key features of the Dew Point Calculator

Solves in every direction

Dew point, relative humidity or air temperature — whichever you are missing.

Why dew point beats humidity

80 percent at 5 °C is dry and 80 percent at 30 °C is oppressive — dew point does not move like that.

Comfort scale

Dry through to oppressive, with the dew point ranges people actually notice.

Condensation risk

Any surface below the dew point collects water, which is why windows fog and drinks bead.

Derived values included

Absolute humidity, vapour pressure and wet bulb temperature from the same inputs.

How to use the Dew Point Calculator

  1. 1

    Choose what to solve for

    Dew point, relative humidity or air temperature.

  2. 2

    Enter the other two

    Temperature in Celsius or Fahrenheit, humidity as a percentage.

  3. 3

    Read the result

    Plus absolute humidity, vapour pressure and wet bulb temperature.

  4. 4

    Check the comfort scale

    Where the dew point sits from dry through to oppressive.

Frequently asked questions

The temperature air must cool to for water vapour to start condensing. It is an absolute measure of moisture content, unlike relative humidity.

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