Using the Dew Point Calculator
Enter temperature in Celsius and relative humidity as a percentage. At 100% relative humidity, the dew point equals the air temperature in this formula. At a lower humidity, the calculated dew point is lower than the current air temperature.
Worked example
Use the example inputs below to reproduce this result. These are the form's starting values, not recommended targets. Changing your inputs updates your result above; this worked example stays fixed for comparison. Results are rounded for display.
Example inputs
- Air temperature (°C)
- 25
- Relative humidity (%)
- 60
Example result
- Dew point (°C)
- 16.697664
Method and assumptions
Magnus approximation over liquid water. Uses coefficients 17.625 and 243.04°C; not a frost-point calculation.
Use temperature and humidity from the same conditions
Temperature and relative humidity should describe the same place and time. Combining an indoor temperature with an outdoor humidity reading can produce a number that does not represent either location. The model explains the entered conditions; it does not retrieve observations, forecast changes or replace local weather guidance.
Common question
Why can relative humidity change while dew point stays similar?
Relative humidity depends on temperature as well as moisture. Warming air without substantially changing its moisture can lower relative humidity while leaving dew point approximately unchanged. The two measures therefore describe related but different aspects of the air.
Guide updated .