What does the Dew Point Calculator measure?

It calculates the dew point — the temperature air would need to cool to at constant pressure for it to become saturated and start condensing into dew — from an air temperature and a relative humidity reading.

What formula does the Dew Point Calculator use?

It uses the Magnus approximation: γ = ln(RH/100) + a·T/(b+T) and Td = b·γ/(a−γ), with a = 17.27 and b = 237.7, which is accurate for typical outdoor temperature and humidity ranges.

Why does higher humidity raise the result in the Dew Point Calculator?

Air that is already close to saturated needs less cooling to reach 100% humidity, so a higher relative humidity at the same temperature produces a higher, closer-to-air-temperature dew point.

Can the Dew Point Calculator work in Fahrenheit?

Yes. Switch the unit toggle to US (°F) and enter temperature in Fahrenheit — the tool converts to Celsius internally, computes the dew point, and shows the result in both °C and °F.

Does the Dew Point Calculator upload my readings?

No. The Dew Point Calculator runs entirely in your browser. The temperature and humidity you enter never leave your device and are not uploaded to ArrayKit.

What counts as a comfortable dew point in the Dew Point Calculator's rating?

Roughly 10–15°C reads as comfortable, 18–23°C starts feeling humid, and above 24°C is labeled humid to oppressive — the exact NWS-style scale most meteorologists use for outdoor comfort.

Dew Point Calculator Online

Calculate dew point from air temperature and relative humidity right in your browser, with a comfort rating for the result.

The Dew Point Calculator runs entirely in your browser. The temperature and humidity figures you enter never leave your device and nothing is uploaded to ArrayKit.

Open the Heat Index Calculator

About Dew Point Calculator

Dew Point Calculator finds the temperature at which air becomes saturated with moisture and dew starts to form, using the standard Magnus formula. Enter an air temperature and relative humidity in either metric (°C) or US (°F) units, and it converts internally to compute the dew point instantly. Alongside the numeric result you get a plain-language comfort rating — from dry to oppressive — so you can judge how muggy the air will actually feel, not just read a raw number. It is useful for weather enthusiasts, HVAC technicians, greenhouse growers, and anyone tracking condensation risk on windows, pipes, or equipment. Everything runs locally in your browser, so the figures you enter stay on your device.

Features

Computes dew point from air temperature and relative humidity using the Magnus formula
Supports both metric (°C) and US/imperial (°F) units with a single toggle
Converts between unit systems automatically before calculating
Shows the result in both Celsius and Fahrenheit side by side
Adds a plain-language comfort rating from Dry to Oppressive
Copies a full result summary with one click
Flags invalid humidity entries below 0% or above 100% with a clear error
Runs entirely in your browser with no weather data sent anywhere

How to use the Dew Point Calculator

Choose metric (°C) or US (°F) units
Enter the air temperature
Enter the relative humidity percentage
Read the dew point and comfort rating, then copy the summary

Example

Input

30°C, 70% RH

Output

Dew point: 23.9°C

The Magnus formula converts temperature and relative humidity into a dew point in °C and °F.

Common errors & troubleshooting

Relative humidity entered as a decimal like 0.7 instead of 70. — Enter humidity as a whole percentage from 0 to 100, not a fraction — type 70 for 70% RH, not 0.7.
Dew point reads higher than the air temperature. — That is not physically possible — double-check the temperature and humidity values, since dew point can never exceed the current air temperature.
Result looks off after switching units. — Re-enter the value in the newly selected unit — the field does not auto-convert a number you already typed, only the calculation does.

Frequently asked questions

What does the Dew Point Calculator measure?: It calculates the dew point — the temperature air would need to cool to at constant pressure for it to become saturated and start condensing into dew — from an air temperature and a relative humidity reading.
What formula does the Dew Point Calculator use?: It uses the Magnus approximation: γ = ln(RH/100) + a·T/(b+T) and Td = b·γ/(a−γ), with a = 17.27 and b = 237.7, which is accurate for typical outdoor temperature and humidity ranges.
Why does higher humidity raise the result in the Dew Point Calculator?: Air that is already close to saturated needs less cooling to reach 100% humidity, so a higher relative humidity at the same temperature produces a higher, closer-to-air-temperature dew point.
Can the Dew Point Calculator work in Fahrenheit?: Yes. Switch the unit toggle to US (°F) and enter temperature in Fahrenheit — the tool converts to Celsius internally, computes the dew point, and shows the result in both °C and °F.
Does the Dew Point Calculator upload my readings?: No. The Dew Point Calculator runs entirely in your browser. The temperature and humidity you enter never leave your device and are not uploaded to ArrayKit.
What counts as a comfortable dew point in the Dew Point Calculator's rating?: Roughly 10–15°C reads as comfortable, 18–23°C starts feeling humid, and above 24°C is labeled humid to oppressive — the exact NWS-style scale most meteorologists use for outdoor comfort.

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