﻿ Specific Humidity Calculator

Specific Humidity Calculator

 Enter the Partial Pressure of Water Vapor, PW: lbs/sq. ft Enter the Total Pressure of Air/Water Vapor Mixture, P: lbs/sq. ft

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The Specific Humidity Calculator calculates the specific humidity of the air of an environment based on the partial pressure of the water vapor of the air and the total pressure of the water vapor/air mixture of the air.

Specific humidity is the ratio of the pressure of water vapor to the rest of the pressure of the air besides the water vapor. Sometimes it is referred to as the humidity ratio. The best way to think of specific humidity is just the partial pressure of water vapor only in the air to the total combined pressure of all the other fluid particles in the air. Therefore, it's the ratio of water vapor to everything else combined in the air.

The factors which affect specific humidity are the partial pressure of water vapor, PW, and the total pressure of the water vapor/air mixture, P. The greater the partial pressure of water vapor, the greater the specific humidity. The lesser the partial pressure, the smaller the humidity.

Note that the partial pressure of water vapor cannot be a greater value than the total pressure of the water vapor/air mixture. Being that the total pressure comprises both partial water vapor and the pressure of all other particles in the air, the total pressure must always be greater than the partial pressure. If a value is entered into the calculator where the partial pressure is greater than the total pressure, an error message will be sprung, stating this is an error.

Partial and total pressures, PW and P, are computed in unit lbs/sq. ft. However, if you want to change these and use different units, the answer will still work out as the same, as long as you use equal unit measurement for both pressures.

To use this calculator, a user just enters the partial pressure, PW, and the total pressure, P, and then clicks the 'Calculate' button, and the resultant specific humidity value will be automatically computed. It is in percentage value.