Calculators
Dew Point Calculator
Estimate dew point from air temperature and relative humidity locally in your browser.
Dew point is estimated with the Magnus formula from air temperature and relative humidity. Values are calculated privately in your browser.
Estimate when air moisture may condense.
Enter air temperature and relative humidity in Celsius or Fahrenheit. The calculator uses the Magnus approximation to estimate the temperature at which the air would become saturated and condensation could begin. A higher dew point means more moisture in the air; a result close to the air temperature indicates high relative humidity. This is an atmospheric estimate, not a weather forecast, and your values are calculated locally without being uploaded or stored.
Frequently Asked Questions
Everything you need to know about this tool, how it works, and privacy.
What formula does this dew point calculator use?
The calculator uses the Magnus approximation. It first calculates γ = ln(RH ÷ 100) + (a × T) ÷ (b + T), then dew point = b × γ ÷ (a − γ), with T in Celsius, a = 17.625, and b = 243.04. This is a practical atmospheric estimate rather than an exact measurement.
Can I calculate dew point in Celsius or Fahrenheit?
Yes. Choose Celsius or Fahrenheit before entering the air temperature. The calculator converts Fahrenheit to Celsius for the formula, then returns the dew point in the unit you selected. Relative humidity is always entered as a percentage greater than 0 and no more than 100.
How should I interpret the dew point result?
Dew point is the temperature at which the air would become saturated if it cooled without changing its moisture content. A higher dew point means more moisture in the air. When the dew point is close to the current air temperature, relative humidity is high and condensation is more likely if surfaces cool to that temperature.
Do my temperature and humidity values stay private?
Yes. The calculation runs locally in your browser. CodeASystem does not upload or store the temperature or relative humidity you enter.