Dew Point Calculator
Calculate the dew point from temperature and relative humidity using the Magnus-Tetens formula. Shows comfort band (dry, sticky, muggy, oppressive).
Dew point conditions
Dew point
59.7 °F
15.4 °C
Comfort: Comfortable- Air temperature
- 80 °F
- Relative humidity
- 50%
- Depression (T minus DP)
- 20.3 °F
- Dew point (other unit)
- 15.4 °C
Frequently Asked Questions about the Dew Point Calculator
What is the dew point?
The dew point is the temperature to which air must be cooled at constant pressure for water vapor to condense into liquid water (dew). It is a direct measure of how much moisture is in the air, unlike relative humidity, which depends on the temperature.
What formula does this calculator use?
The Magnus-Tetens approximation used by the US National Weather Service. With T in degrees Celsius and RH as a percent, alpha = ln(RH/100) + (17.625 * T) / (243.04 + T), and dew point (°C) = (243.04 * alpha) / (17.625 - alpha). Accuracy is within about 0.4 °C for typical weather conditions.
Why is dew point a better comfort indicator than humidity?
Relative humidity changes with temperature, so 60% RH at 50 °F feels nothing like 60% RH at 90 °F. Dew point is an absolute measure of moisture, so the same dew-point value feels the same regardless of air temperature. Most weather forecasters track dew point for that reason.
What do the comfort bands mean?
Below 50 °F is dry and comfortable. From 50 to 60 °F is comfortable for most people. From 60 to 65 °F starts to feel sticky. From 65 to 70 °F is muggy. At 70 °F and above the air feels oppressive, and outdoor exertion becomes uncomfortable.
What is the dew point depression?
The dew point depression is the difference between the air temperature and the dew point (T minus DP). A small depression (a few degrees) means the air is close to saturation, so fog, dew, or cloud cover are likely. A large depression means dry air with low risk of condensation.
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