Dew Point Calculator

How to use the dew point calculator

1. Enter the air temperature and choose °C or °F.
2. Enter the relative humidity as a percentage.
3. Read the dew point and the comfort guide.
4. Copy the link to save or share it.

What the dew point is

The dew point is the temperature the air would have to cool to for water vapour to condense, the point at which dew, fog, or clouds start to form. It is a direct measure of how much moisture is in the air, which makes it a better guide to how humid it feels than relative humidity alone. A high dew point means muggy, sticky air; a low one means dry, comfortable air, so it is a good comfort humidity guide. This dew point calculator turns relative humidity to dew point, working the dewpoint out from the temperature and relative humidity with a clear dew point formula.

The Magnus formula

The tool uses the Magnus formula with the Alduchov and Eskridge coefficients, a widely used and accurate approximation. It combines the temperature and the relative humidity into an intermediate value, then solves for the dew point. The formula is shown in the result so you can see the maths, and it holds well across the everyday range of weather conditions.

Dew point and comfort

Unlike relative humidity, which changes as the air warms and cools through the day, the dew point stays fairly steady and tracks how the air actually feels. As a rough guide, a dew point below about 10°C (50°F) feels dry, the mid-teens Celsius feel comfortable, and above about 20°C (68°F) the air feels oppressive and sweat struggles to evaporate. The tool labels your result with this comfort scale.

A worked example

At an air temperature of 25°C with 60% relative humidity, the dew point is about 16.7°C. That sits at the sticky end of comfortable, so the air would start to feel humid.

FAQ

What is the dew point?

The dew point is the temperature to which air must cool for moisture to condense. It measures the actual moisture in the air, so it indicates humidity better than the relative-humidity percentage.

Is a higher dew point more humid?

Yes. A higher dew point means more moisture in the air and a muggier feel. Below about 10°C (50°F) the air feels dry; above about 20°C (68°F) it feels oppressive.

How is the dew point different from relative humidity?

Relative humidity changes as temperature changes through the day, while the dew point stays fairly constant and reflects the real moisture content, which is why it tracks comfort more reliably.

What formula does this use?

The Magnus formula with the Alduchov and Eskridge coefficients, a standard and accurate approximation shown in the result.

Is my information private?

Yes. Everything is calculated in your browser and nothing you enter is uploaded or saved.