Humidity Calculator

The Magnus approximation with Sonntag coefficients is accurate to within about 0.4 C for temperatures between -40 C and 50 C and relative humidity above 5%. For most indoor comfort, HVAC, and weather applications, this is more than sufficient.

The simple Magnus form is most reliable for typical comfort ranges (0 C to 50 C). Below freezing, frost point replaces dew point, and different coefficients are needed. The results below 0 C should be treated as rough estimates.

Dew point is a better indicator of mugginess than relative humidity alone. A dew point above 20 C feels uncomfortably humid, while below 10 C feels dry. Indoor surfaces colder than the dew point (like windows in winter) will collect condensation, which can lead to mold growth.

This calculator requires Celsius input. To convert from Fahrenheit: subtract 32 and multiply by 5/9. For example, 77 F = (77 - 32) x 5/9 = 25 C.

Most people feel comfortable with indoor dew points between 10 C and 16 C (50 F to 60 F). Above 18 C feels sticky, and below 5 C feels very dry and may cause skin irritation and static electricity.

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