1. The pressure is assumed to be 101.3 kPa (kiloPascals).
2. A conversion factor is calculated: A = 0.00066 (1.0 + 0.00115 Twb)
3. The saturation vapor pressure is calculated at Twb: eswb
= e[(16.78 Twb - 116.9)/(Twb + 237.3)]
4. The water vapor pressure is calculated: ed = eswb
- A P (Tdb - Twb)
5. The saturation vapor pressure is calculated at Tdb: esdb
= e[(16.78 Tdb - 116.9)/(Tdb + 237.3)]
6. The relative humidity is then calculated: RH = 100 ed/esdb