Dew Point Calculator

The dew point is the temperature at which air becomes saturated and water starts to condense. It is a better measure of how humid it feels than relative humidity.

How to use the Dew Point Calculator

Enter the air temperature and choose the unit.
Enter the relative humidity.
Read the dew point and how humid it will feel.

How it works

The dew point is calculated with the Magnus formula:

γ = ln(RH/100) + aT/(b + T), T_d = bγ / (a − γ)

with a = 17.625 and b = 243.04 °C. Comfort levels (dew point in °F): below 50 dry, 50–59 comfortable, 60–64 somewhat humid, 65–69 muggy, 70–74 oppressive, 75+ extremely oppressive.

Dew point (°C) at 25 °C air temperature

Relative humidity	Dew point
20%	0.5 °C / 32.9 °F
30%	6.2 °C / 43.2 °F
40%	10.5 °C / 50.8 °F
50%	13.9 °C / 56.9 °F
60%	16.7 °C / 62.1 °F
70%	19.1 °C / 66.5 °F
80%	21.3 °C / 70.4 °F
90%	23.2 °C / 73.8 °F
100%	25 °C / 77 °F

Frequently asked questions

What is a comfortable dew point?

Dew points below about 60 °F (16 °C) feel comfortable for most people; above 65 °F (18 °C) feels muggy.

Can the dew point be higher than the temperature?

No. When the air cools to the dew point it is saturated (100% humidity) and fog, dew or condensation forms.

Why does dew form at night?

Surfaces cool after sunset. When they drop below the dew point, water vapour condenses on them as dew (or frost below freezing).