Free Dew Point Calculator Online
Use this free dew point calculator to find the temperature at which moisture condenses from the air. Enter the air temperature and relative humidity, and the dew point calculator instantly shows the dew point, comfort level, and whether condensation is likely on common surfaces.
Dew Point
Enter temperature and humidity
How the Dew Point Calculator Works
The dew point calculator uses the Magnus formula, a well-established approximation for the dew point temperature. Given air temperature (T) and relative humidity (RH), it computes alpha = (17.27 x T) / (237.7 + T) + ln(RH/100), then Td = (237.7 x alpha) / (17.27 - alpha). This dew point calculator provides accurate results across typical environmental conditions.
For example, at 75°F (23.9°C) and 60% humidity, the dew point calculator returns about 60°F (15.6°C). This means surfaces cooled below 60°F will collect condensation. The gap between air temperature and dew point indicates how dry the air feels — a larger gap means drier, more comfortable air.
The dew point calculator also categorizes comfort: below 50°F dew point is pleasant, 50-59°F is comfortable, 60-64°F is sticky, 65-69°F is muggy, and above 70°F is oppressive. This is why dew point is considered a better comfort metric than relative humidity alone.
Dew Point Comfort Scale
The dew point calculator shows your comfort level automatically.
Why Dew Point Matters
Comfort
Dew point is a better comfort indicator than humidity alone. 90% RH at 50°F is pleasant, but 50% RH at 95°F feels oppressive. The dew point calculator cuts through the confusion.
Building Science
Moisture damage occurs when warm humid air contacts cold surfaces. The dew point calculator helps builders and homeowners identify condensation risk in walls, attics, and basements.
Aviation
Pilots monitor dew point to predict fog, clouds, and icing. When temperature approaches the dew point, visibility can drop rapidly. The dew point calculator helps with pre-flight planning.
Frequently Asked Questions
Disclaimer: This dew point calculator uses the Magnus formula approximation. Accuracy may vary at extreme temperatures. For critical applications, consult psychrometric charts or professional instruments.
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