Enter either the mass of the dry and wet air or the partial pressures of the dry and wet air into the calculator to determine the humidity ratio.

Humidity Ratio Formula

The following two formulas can be used to calculate a humidity ratio.

x = mw / md

  • Where x is the humidity ratio
  • mw is the mass of the water vapor
  • md is the mass of the dry air

x = .62198 * pw / (pa-pw)

  • Where x is teh humidity ratio
  • pw is the partial pressure of water vapor in moist air
  • pa is the atmospheric pressure of moist air.

Humidity Ratio Definition

A humidity ratio is defined as the ratio of the mass of water vapor in humid air over the mass of dry air in a body of air.

Humidity Ratio Example

How to calculate a humidity ratio?

First, you must determine the mass of the water vapor in the humid air. For this example, the mass of the water vapor is experimentally found to be 50kg.

Next, the mass of the dry air must be calculated or found. Similar to the step above, the dry air mass is found to be 100kg.

Finally, using the formula above, the humidity ratio is found to be:

x = 50/100 = .50

Most often this ratio is expressed as a percentage. This can be done by multiplying the result by 100.

.50 *100 = 50%.

humidity ratio calculator