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.
= 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
📌 Calculated with the Magnus formula (coefficients 17.62 / 243.12 °C), accurate to a few tenths of a degree for ordinary weather conditions. Absolute humidity tells you the actual amount of water vapor in the air — unlike relative humidity, it does not change when the temperature changes.
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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.
Frequently asked questions
Most people start noticing mugginess at a dew point around 60°F, and 65°F and above feels distinctly humid and sticky to nearly everyone. At 70°F+ the air is oppressive — typical of the Gulf Coast in midsummer. Below 55°F almost no one perceives the air as humid, no matter what the relative humidity says.
Relative humidity compares the moisture in the air to the maximum the air could hold at its current temperature, so it swings up and down as the temperature changes even when the moisture stays constant. Dew point measures the actual moisture content directly. That is why 100% humidity on a 40°F morning feels crisp while 55% humidity on a 90°F afternoon feels sweltering — the dew points are about 40°F and 72°F.
There is no single magic number — fog and dew form whenever the air temperature falls to the dew point, so the water vapor condenses into droplets. If the evening dew point is 60°F and overnight cooling drops the air to 60°F, expect fog in low spots and wet grass by morning. The smaller the gap between temperature and dew point, the higher the fog risk.
For comfort and healthy air, aim for an indoor dew point of roughly 40–55°F. Above about 60°F indoors, the air feels clammy and dust mites and mold thrive; below about 30°F, skin, eyes, and airways can feel dry. At a typical 70°F room temperature, that comfortable range corresponds to roughly 35–60% relative humidity.
Any surface colder than the dew point of the surrounding air will collect condensation. A glass of iced tea sits well below the dew point on a humid day, so water vapor condenses onto it. The same happens on window glass in winter: warm indoor air touching a cold pane cools below its dew point. Lowering indoor humidity lowers the dew point and stops the fogging.
Cite this calculator
APACalcBrew. (2026). Dew Point Calculator. https://calcbrew.com/dew-point-calculator
MLA“Dew Point Calculator.” CalcBrew, 2026, calcbrew.com/dew-point-calculator.
Link to https://calcbrew.com/dew-point-calculator. Results are estimates; cite the underlying formula or data source for academic work.