Dew Point Calculator
Dew point from temperature and humidity.
Enter your values
ⓘ Live results
Results
- Dew point
- 18.19 °C
- In Fahrenheit
- 64.74 °F
- Comfort level
- Humid
- Spread from air temp
- 5.81 °C
- Fog likely if temp falls to
- 18.2 °C
Working
- 1α = ln(70/100) + (17.625 × 24)/(243.04 + 24) = 1.2274
Quick answer
Dew point is the temperature at which air becomes saturated; above 20°C (68°F) most people find the air oppressive.
Td = (b·α) ÷ (a − α), α = ln(RH/100) + aT/(b+T)
How to use the Dew Point Calculator
- 1Enter the air temperature in Celsius.
- 2Enter relative humidity.
- 3Read the dew point and comfort level.
Worked example
Using the values the calculator loads with:
Inputs
- Air temperature24 °C
- Relative humidity70 %
Results
- Dew point18.19 °C
- In Fahrenheit64.74 °F
- Comfort levelHumid
- Spread from air temp5.81 °C
- Fog likely if temp falls to18.2 °C
- α = ln(70/100) + (17.625 × 24)/(243.04 + 24) = 1.2274
Frequently asked questions
Why is dew point better than humidity?
Relative humidity depends on temperature; dew point is an absolute measure of moisture, so 20°C dew point feels muggy anywhere.
When does condensation form?
When a surface is at or below the dew point — that's why cold glasses sweat and windows fog.
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.