Absolute Humidity Calculator
Estimate water vapor per cubic meter, mixing ratio, vapor pressure and air density.
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Express atmospheric moisture as mass and pressure
Enter temperature, relative humidity and station pressure. The calculator estimates saturation vapor pressure, applies relative humidity to obtain actual vapor pressure and converts it into grams of water vapor per cubic meter. It also reports a water-vapor mixing ratio per kilogram of dry air and an ideal moist-air density so the different moisture measures can be compared.
Use station pressure and suitable observations
Relative humidity changes when temperature changes even if the water-vapor amount remains constant. The calculation is intended for ordinary atmospheric conditions and uses ideal-gas and saturation-pressure approximations. Precision laboratory, industrial or aviation work can require a specified standard, calibrated instruments and corrections beyond this browser estimate.
Frequently asked questions
How does absolute humidity differ from relative humidity?
Absolute humidity is water-vapor mass per volume, while relative humidity compares vapor pressure with saturation at the current temperature.
Why is station pressure requested?
Pressure is used for mixing ratio and moist-air density calculations.
Does warming air always add moisture?
No. Relative humidity can fall as temperature rises even when vapor amount stays unchanged.