pound per pound of dry air
Humidity ratioexact by definition
The pound per pound of dry air is dimensionally identical to kg/kg, so the factor is exactly 1. US psychrometric charts label the vertical axis lb water per lb dry air, and comfort conditions land between about 0.007 and 0.012.
Watch out: Written lbw/lbda or lb/lb, and always per pound of DRY air, not per pound of moist air. That is the definition of humidity ratio and the reason it can exceed the mass fraction of water in the mixture.
| 1 | 1,000 |
One pound per pound of dry air in every humidity ratio unit
| 1,607,860,000 | part per billion by volume (moisture) (ppbv) | |
| 1,000,000,000 | microgram per kilogram of dry air (μg/kg) | |
| 1,607,860 | part per million by volume (moisture) (ppmv) | |
| 1,000,000 | milligram per kilogram of dry air (mg/kg) | |
| 7,000 | grain per pound of dry air (gr/lb) | |
| 1,000 | gram per kilogram (g/kg) | |
| 1 | kilogram per kilogram (kg/kg) | |
| 1 | pound per pound of dry air (lb/lb)this unit |
Solvers that use humidity ratio