Dew Point Calculator
Dew point estimates the temperature at which air with the entered water-vapour content reaches saturation under the approximation used. It helps with condensation risk awareness.
How to use this calculator
- Enter air temperature (°c), relative humidity (%) using the same measurement window and units.
- Check the result and intermediate values, then change one input at a time when comparing scenarios.
- Keep the stated scope and assumptions attached to any result you share.
Formula and method
Magnus approximation: γ = ln(RH/100) + aT/(b+T); dew point = bγ/(a−γ), using a = 17.62 and b = 243.12 °C.
- The estimated dew point is about 12.5°C.
- This is an approximation for common atmospheric conditions. Pressure, sensor accuracy, unusual conditions and surface temperature patterns can affect condensation assessment.
Worked examples
Worked example
Air at 22°C and 55% relative humidity.
The estimated dew point is about 12.5°C.
The estimated dew point is about 12.5°C.
Understanding the result
The estimated dew point is about 12.5°C.
This is an approximation for common atmospheric conditions. Pressure, sensor accuracy, unusual conditions and surface temperature patterns can affect condensation assessment.
Important notes
This is an approximation for common atmospheric conditions. Pressure, sensor accuracy, unusual conditions and surface temperature patterns can affect condensation assessment.
Use measured inputs or documented assumptions, and validate important decisions with the appropriate source specifications or professional guidance.
Frequently asked questions
Is dew point the same as relative humidity?
No. Dew point is a temperature; relative humidity is a percentage relative to saturation at the current temperature.
Does this predict mold?
No. It estimates a moisture-related temperature threshold, not mold risk or indoor air quality.
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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.