Dew Point Calculator
Want to know how muggy it really is? Enter the temperature and relative humidity to get the dew point — the single best measure of how humid the air feels — with a comfort scale and absolute humidity. Or flip it around and find the humidity from a known dew point.
At 85°F and 60% humidity the dew point is
69.6°F
= 20.9°C · absolute humidity ≈ 17.6 g of water per m³ of air
💧 Comfort level: Uncomfortable
Distinctly humid and sticky for almost everyone. Air conditioning and dehumidifiers earn their keep at this level.
Dew point comfort scale
| Dew point | How it feels |
|---|---|
| Below 50°F | Dry and comfortable |
| 50–60°F | Pleasant |
| 60–65°F | Sticky |
| 65–70°F | Uncomfortable |
| 70°F and up | Oppressive |
Why dew point beats relative humidity
Relative humidity is relative to the temperature: warm air can hold far more moisture than cold air, so the same amount of water vapor reads as 90% humidity at dawn and 45% by mid-afternoon — while the air's actual moisture content never changed. That makes RH a poor answer to "how humid does it feel?"
The dew point cuts through this. It is the temperature the air would have to cool to for its moisture to start condensing — and it depends only on how much water vapor is actually in the air. A dew point of 70°F feels oppressive at 8 AM and at 3 PM alike, whatever the relative humidity happens to read. That's why meteorologists reach for the dew point when they want to describe mugginess.
The same number explains condensation: any surface cooler than the dew point — window glass in winter, a soda can in summer, grass on a clear night — pulls water straight out of the air. If the overnight temperature is forecast to drop to the dew point, expect fog and wet windshields by morning.
The Magnus formula and a worked example
The calculator uses the Magnus approximation, the standard formula in meteorology. With the temperature T in °C and relative humidity RH in percent:
γ = ln(RH/100) + 17.62·T / (243.12 + T)
Td = 243.12·γ / (17.62 − γ)
Example: a summer day at 90°F (32.2°C) and 60% humidity. First γ = ln(0.60) + 17.62 × 32.2 / (243.12 + 32.2) = −0.511 + 2.061 = 1.550. Then Td = 243.12 × 1.550 / (17.62 − 1.550) ≈ 23.5°C ≈ 74°F — an oppressive, tropical-feeling dew point, even though "60% humidity" sounds moderate on paper. The Fahrenheit interface converts to Celsius internally and back again, so you can work in either unit.
More weather tools
The dew point tells you how muggy it is; the heat index calculator combines that moisture with the temperature into a feels-like reading and an official NWS danger category. In winter, the wind chill calculator handles the other extreme. And for quick °F ↔ °C math, there's the temperature converter.