- Dew point
- 16.7 °C
How it works
Condensation depends on the surface temperature
A cold window can reach the dew point while the room air stays warmer. Compare the calculated dew point with the surface temperature when investigating condensation; room temperature alone cannot explain where droplets first appear.
Keeping humidity measurements consistent
Dew point, relative humidity, and air temperature describe related aspects of moisture in air. Choose the unknown quantity and enter the other measurements using compatible units. Relative humidity depends on temperature, so the same moisture content can correspond to different percentages as air warms or cools. The calculator applies the selected approximation and does not replace a measured atmospheric observation.
Dew point: formula and assumptions
γ = ln(RH/100)+17.625T/(243.04+T); dew point = 243.04γ/(17.625−γ).
Magnus approximation over liquid water, within the displayed temperature range.
Relative humidity or air temperature: formula and assumptions
RH=100 exp[aTd/(b+Td)−aT/(b+T)], with a=17.625, b=243.04.
The same liquid-water Magnus approximation is used in each direction.
Worked example
Using the Dew point example:
- Air temperature (°C)
- 25
- Relative humidity (%)
- 60
γ = ln(RH/100)+17.625T/(243.04+T); dew point = 243.04γ/(17.625−γ).
Example result
Dew point: 16.7 °C
These are illustrative inputs. Change the values to explore a different scenario.
Formula references
References explain the underlying methods; they do not imply endorsement or individual professional review of Finflo.
Common questions
What does the dew point describe?
It is the temperature at which the modeled air reaches saturation when cooled at the assumed moisture content.
Does the same approximation apply in every atmospheric condition?
No. This implementation uses the stated liquid-water Magnus coefficients within its displayed range, rather than every possible ice or pressure condition.
Prepared by Finflo. See our methodology and editorial policy.