Dew Point Calculator
Humidity Comfort Estimation
Dew Point
--
Ready for Calculation
Enter temperature and relative humidity to calculate the dew point.
Understanding Dew Point
Dew point is the temperature at which air becomes fully saturated with moisture and water begins to condense — visible as dew, fog, or frost. Unlike relative humidity, dew point is a direct, absolute measure of how much moisture is actually in the air, which makes it a far better indicator of how "muggy" the air will feel.
Why Not Just Use Humidity?
Relative humidity depends on temperature — 50% humidity at 60°F feels dry, while 50% at 95°F feels oppressive. Dew point stays consistent regardless of temperature, making it the more reliable comfort measure.
The Magnus Formula
This calculator uses the Magnus-Tetens approximation, a well-established formula meteorologists use to derive dew point from temperature and relative humidity.
Reading Dew Point Comfort Levels
Below 55°F (13°C): Dry and comfortable. 55-65°F (13-18°C): Comfortable to slightly humid. 65-70°F (18-21°C): Getting sticky. 70-75°F (21-24°C): Uncomfortably humid. Above 75°F (24°C): Oppressive, tropical-feeling air.
Frost Warning
If the dew point is expected to drop to or below freezing overnight, frost is likely to form on exposed surfaces.
Key Takeaways
- Dew Point Can't Exceed Air Temperature: The dew point is always less than or equal to the current air temperature — when they're equal, the air is fully saturated (100% relative humidity).
- Better Than Humidity Alone: Meteorologists prefer dew point over relative humidity for describing how muggy conditions actually feel.
- Fog Formation: Fog tends to form overnight when the air temperature drops to meet the dew point.