Dew Point Calculator
The dew point temperature is the temperature at which air becomes saturated with water vapor, causing condensation to form. It is widely used in meteorology, HVAC engineering, and agriculture because it gives a direct, absolute measure of atmospheric moisture content. Unlike relative humidity, which rises and falls as temperature changes through the day, the dew point remains relatively stable and directly reflects the actual amount of water vapor in the air. Meteorologists and comfort researchers consider the dew point a more reliable indicator of how humid conditions actually feel. When the dew point climbs above 60°F (16°C), most people begin to notice discomfort; above 70°F (21°C) the air feels oppressively muggy; and dew points above 75°F (24°C) are associated with serious health risks during exertion. This calculator uses the Magnus formula, a widely accepted approximation for meteorological dew point calculations. Enter the current air temperature in degrees Celsius and the relative humidity percentage to get the dew point in both Celsius and Fahrenheit, along with a comfort classification.
Dew point: -- °C (-- °F)
Dew point comfort classification
| Dew point (°C) | Dew point (°F) | Comfort level |
|---|---|---|
| Below 10°C | Below 50°F | Dry and comfortable |
| 10-16°C | 50-60°F | Comfortable |
| 16-18°C | 60-65°F | Slightly humid |
| 18-21°C | 65-70°F | Humid, some discomfort |
| 21-24°C | 70-75°F | Very humid, uncomfortable |
| Above 24°C | Above 75°F | Oppressive, potentially dangerous |
Why dew point matters
Meteorologists prefer dew point over relative humidity when describing moisture because it is an absolute measure: 15°C dew point means the same thing regardless of air temperature. In contrast, 60% relative humidity means something quite different at 10°C (cool and comfortable) versus 35°C (extremely oppressive).
Dew point is also essential in HVAC design, greenhouse management, and food storage, where condensation on surfaces can cause damage or mold growth.
Dew point: frequently asked questions
What is the dew point?
The dew point is the temperature to which air must be cooled (at constant pressure and humidity) for water vapor to condense into liquid water. A higher dew point means more moisture in the air. When the dew point equals the air temperature, relative humidity is 100% and fog or dew can form.
What formula is used?
This calculator uses the Magnus formula to estimate dew point: first compute gamma = (17.625 * T) / (243.04 + T) + ln(RH/100), then dew point = (243.04 * gamma) / (17.625 - gamma). This is an approximation valid for typical atmospheric conditions between -40°C and 60°C.
What dew point feels comfortable?
Dew points below 10°C (50°F) feel dry and comfortable. Between 10°C and 16°C (50-60°F) feels pleasant. Between 16°C and 21°C (60-70°F) begins to feel humid. Above 21°C (70°F) feels oppressively humid, and above 24°C (75°F) is considered dangerous for outdoor activity.
How is dew point different from relative humidity?
Relative humidity is the percentage of the maximum moisture the air can hold at a given temperature. Dew point is an absolute measure of moisture content and does not change with temperature. Dew point is generally considered a better indicator of how humid air feels, because relative humidity changes through the day as temperature rises and falls.
Can dew point be higher than air temperature?
No. The dew point can equal the air temperature (when relative humidity is 100%) but cannot exceed it. A relative humidity reading above 100% would indicate measurement error or supersaturation, which is a rare atmospheric phenomenon.
References
- August, E.F. (1828). Ueber die Berechnung der Expansivkraft des Wasserdunstes. Annalen der Physik und Chemie.
- NOAA National Weather Service. "Relative Humidity and Dew Point." weather.gov
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.