Dew Point Calculator

Solve for Dew Point, Temperature, or Humidity. Calculates comfort thresholds, absolute humidity, and Lifting Condensation levels.

Inputs

Solve For

Unit

Air Temperature (°C)

Relative Humidity (%)

Calculated Target values

16.7°C

Dew Point

25.0°C / 77.0°F

Air Temp

60.0%

Relative Humidity

Meteorological Details

Absolute Humidity:13.81 g/m³

Dew Point Spread:8.3°C below temp

Cloud Base Height:~1038m (3407ft)

Comfort Level:Comfortable

Comfort Reference Table

Below 10°C (50°F)Very Dry / Refreshing

10–13°C (50–55°F)Comfortable / Dry

13–16°C (55–61°F)Comfortable

18–21°C (64–70°F)Slightly Humid

21–24°C (70–75°F)Humid / Muggy

Above 24°C (75°F)Oppressively Humid / Wet

How dew point variables are solved

The dew point defines the temperature threshold where moisture in air reaches saturation (100% relative humidity). By utilizing algebraic transpositions of the Magnus formula, this tool allows bidirectional solving for Air Temperature, Relative Humidity, or Dew Point given any other pair of values.

Absolute humidity calculates the true water mass density per unit volume (g/m³). Espy's Lifting Condensation Level (LCL) formula projects cloud base heights based on thermal spreads, while gas pressure factors scale vapor pressures to support industrial piping calculations.

Built and maintained by Meet Shah · Last updated 1 August 2026

What this tool is used for

Working out the temperature at which condensation will form.
Checking whether a surface is at risk of condensation.
Understanding how humid a day will feel from the dew point rather than the humidity.
Comparing two days with the same humidity but different temperatures.
Checking a weather station's dew point figure.

Frequently Asked Questions

What is dew point?: The temperature air must cool to before it becomes saturated and water condenses. Unlike relative humidity it is an absolute measure of moisture content, which is why it predicts comfort so much better — 20 °C dew point feels muggy regardless of what the air temperature is.
Which formula does it use?: The Magnus approximation with the constants a = 17.625 and b = 243.04 °C, which is accurate to about ±0.35 °C across the normal meteorological range. The tool inverts the same relationship to solve for humidity or temperature when the dew point is the known quantity.
How does dew point relate to relative humidity?: RH is the ratio of actual to saturation vapour pressure at the current temperature, so it moves whenever the temperature moves even if no moisture is added or removed. Dew point does not. That is why RH rises overnight while the air is unchanged.
What dew point feels comfortable?: Below 10 °C is dry, 10–16 °C comfortable, 16–20 °C noticeably humid, and above 21 °C oppressive — sweat evaporates too slowly to cool you. Meteorologists quote dew point rather than humidity for exactly this reason: the thresholds are stable across temperatures.
Why does condensation appear on my windows?: Because the glass surface is below the indoor dew point. It is a surface temperature problem, not a humidity problem in itself — either raise the surface temperature with better glazing or lower the indoor dew point with ventilation. Wiping it treats the symptom.

Common errors and gotchas

Confusing relative humidity with dew point, where relative humidity changes with temperature and dew point does not.
Applying the Magnus formula outside its valid range, where it loses accuracy.
Assuming a low relative humidity means comfortable, when a high temperature can still give a high dew point.
Mixing Celsius and Fahrenheit between the inputs.
Reading dew point as a surface temperature rather than a threshold for it.