Dew Point Calculator
Dew point from temperature and humidity.
Enter your values
ⓘ Live results
Results
- Dew point
- 57.7 °F
- In °C
- 14.3
- Surface temperature
- 58 °F
- Condensation risk
- No — surface stays dry
- Margin
- 0.3 °F
Quick answer
Dew point is the temperature at which air becomes saturated and moisture begins to condense on surfaces.
Magnus formula from temperature and RH
How to use the Dew Point Calculator
- 1Enter room temperature and relative humidity.
- 2Enter the surface temperature of the duct, window or wall you are worried about.
- 3Insulate or dehumidify until the surface stays above dew point.
Worked example
Using the values the calculator loads with:
Inputs
- Temperature75 °F
- Relative humidity55 %
- Surface temperature58 °F
Results
- Dew point57.7 °F
- In °C14.3
- Surface temperature58 °F
- Condensation riskNo — surface stays dry
- Margin0.3 °F
Frequently asked questions
Why do ducts sweat?
Chilled supply duct in humid unconditioned space drops below dew point; vapour-sealed insulation fixes it.
Comfort dew point?
Below 55°F feels dry and pleasant; above 65°F feels muggy regardless of temperature.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.