Method
Magnus approximation: γ=ln(RH/100)+aT/(b+T); Td=bγ/(a−γ), using a=17.62 and b=243.12°C.
Everyday worksheet
Dew Point Calculator
Estimate dew point, vapor pressure and temperature spread from air temperature and relative humidity.
The calculation runs locally. Results include the intermediate values, unit conversions and assumptions needed to audit the answer.
Method, assumptions and practical use
How the Dew Point Calculator works
Magnus approximation: γ=ln(RH/100)+aT/(b+T); Td=bγ/(a−γ), using a=17.62 and b=243.12°C. Inputs stay in this browser, and the result table exposes conversions and assumptions for independent checking.
Interpret the result
Dew point is the temperature at which air reaches saturation under the approximation.
Check the assumptions
This water-surface approximation is most appropriate around −45 to 60°C and does not alone prove fog or condensation.
Local calculation
Everything runs in this browser. Inputs are not sent to an external calculator.
Rounding
Displayed values may be rounded for readability while calculations use full floating-point precision unless the tool explicitly uses exact integers.
Scope
This water-surface approximation is most appropriate around −45 to 60°C and does not alone prove fog or condensation.
Simple by design
Three steps to a clearer number.
Enter your details
Use realistic values in each field. You can change them anytime.
Calculate instantly
The formula runs locally, so there is no account or waiting time.
Use the result
Treat the answer as a practical estimate for your next decision.