Dew Point Calculator: Humidity & Comfort

Q: Do °C and °F inputs affect each other?

Yes. They convert both ways using F=1.8C+32F = 1.8C + 32F=1.8C+32. Type in either field and the other updates so you can work in your usual unit.

Dew Point & Humidity

Dew point tells you when moisture will condense. Higher dew point means more moisture in the air and a muggier feel. Use either mode—solve for dew point from temp and humidity, or solve for humidity from temp and dew point.

Core Concepts

Dew Point Mode

You have air temperature and humidity. Get the dew point—the temp at which fog or condensation forms.

Relative Humidity Mode

You have air temperature and dew point (e.g. from a hygrometer). Get the RH percentage.

Comfort Scale

The badge color reflects how humid it feels: green (dry) through yellow (muggy) to red (oppressive). Thresholds are in the article below.

Unit Preference

Toggle °F (US) or °C (Metric) so your primary unit leads. Both inputs stay in sync either way.

Dew Point Calculator: Humidity & Comfort Scale

Calculate dew point from temperature and humidity, or relative humidity from temperature and dew point. Magnus-Tetens formula. Comfort scale for dry, comfortable, muggy, and oppressive. Free—runs locally.

What Is Dew Point?

Dew point is the temperature at which air becomes saturated with moisture and condensation begins. It's useful for weather forecasting, HVAC sizing, and knowing when to expect fog or condensation. Unlike relative humidity—which depends on temperature—dew point is a direct measure of moisture: higher dew point means more water vapor in the air, and a muggier feel.

The Magnus-Tetens Formula

The calculator uses the Magnus-Tetens approximation. First

\gamma(T, RH) = \ln(RH/100) + \frac{bT}{c+T}

where T is air temperature (°C) and RH is relative humidity (0–100). Then

T_d = \frac{c\gamma}{b - \gamma}

gives the dew point in °C. Constants: b = 17.625, c = 243.04. To find RH from T and dew point

T_d

, use

\gamma = \frac{bT_d}{c+T_d}

and

RH = 100 \cdot e^{\gamma - \frac{bT}{c+T}}

Comfort Scale

Dry

Dew point < 50°F (10°C). Low moisture; air feels crisp.
Comfortable

50–60°F (10–15°C). Moderate humidity; most people find this pleasant.
Muggy

60–70°F (15–21°C). Noticeable moisture; less evaporative cooling.
Extremely Humid / Oppressive

> 70°F (21°C). High moisture; sweat does not evaporate well.

Dew Point Calculator FAQ

? What is dew point?

Dew point is the temperature at which air reaches saturation and moisture starts to condense—fog on your glasses, beads on a cold drink. It depends on both air temperature and relative humidity. The formula used here is the Magnus-Tetens approximation:

\gamma = \ln(RH/100) + \frac{bT}{c+T}

, then

T_d = \frac{c\gamma}{b-\gamma}

with b = 17.625, c = 243.04 (Celsius).

? How do I find relative humidity from dew point?

Switch to "Calculate For: Relative Humidity," enter air temperature and dew point in °C or °F (they stay synced), and you get RH %. The inverse of the Magnus-Tetens formula handles it.

? What does the comfort scale mean?

Dew point maps to how humid it feels. Under 50°F (10°C) is dry. 50–60°F is comfortable for most. 60–70°F gets muggy. Above 70°F (21°C) feels oppressive because sweat doesn’t evaporate well.

? Do °C and °F inputs affect each other?

Yes. They convert both ways using

F = 1.8C + 32

. Type in either field and the other updates so you can work in your usual unit.

Dew Point Calculator: Humidity & Comfort Scale

Settings

Air Temperature

Relative Humidity

Dew Point & Humidity

Core Concepts

Dew Point Mode

Relative Humidity Mode

Comfort Scale

Unit Preference

Dew Point Calculator: Humidity & Comfort Scale

What Is Dew Point?

The Magnus-Tetens Formula

Comfort Scale

Dew Point Calculator FAQ

? What is dew point?

? How do I find relative humidity from dew point?

? What does the comfort scale mean?

? Do °C and °F inputs affect each other?

Mathematical Reference Note