Dew Point Calculator
Calculate the dew point temperature from air temperature and relative humidity using the Magnus formula. Shows comfort level.
Dew Point
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In Fahrenheit
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Depression
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Comfort
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What is Dew Point Calculator?
The dew point is the temperature at which air becomes saturated with moisture and water vapor begins to condense. It's a direct measure of atmospheric moisture content and a reliable indicator of how humid and uncomfortable the air feels.
How to use
- 1 Select your temperature unit (°C or °F).
- 2 Enter the current air temperature.
- 3 Enter the relative humidity percentage.
- 4 Click Calculate to get the dew point and comfort level.
- 5 Dew points above 60°F (16°C) start to feel uncomfortable for most people.
Formula
Example calculation
At 30°C and 70% humidity: γ = ln(0.70) + 17.625×30/(243.04+30) = −0.3567 + 1.9347 = 1.578. Td = (243.04 × 1.578) / (17.625 − 1.578) ≈ 23.9°C (75°F) — oppressive.
Frequently asked questions
What is a comfortable dew point?
Dew points below 55°F (13°C) feel dry and comfortable. Between 55–65°F it starts feeling humid. Above 65°F feels sticky; above 75°F is oppressive.
How is dew point different from humidity?
Relative humidity changes with temperature but dew point stays constant. Dew point is a more reliable indicator of absolute moisture in the air.
What does 100% humidity mean?
At 100% relative humidity, the air temperature equals the dew point. Condensation (fog, dew) forms on surfaces.
Can the dew point be higher than the air temperature?
No. The dew point is always equal to or lower than the air temperature. When they're equal, relative humidity is 100%.
Why does the dew point matter for health?
High dew points reduce the body's ability to cool itself by sweating. Combined with high temperatures, this raises heat stress and risk of heat illness.