Enter the dry bulb temperature ( T_dry ) and wet bulb temperature ( T_wet) in C or F,  then click on the Calculate RH button

NOTE: Fine tune this by entering YOUR barometric pressure (i.e. 29.1)
1. The pressure is assumed to be 101.3 kPa (kiloPascals).
2. A conversion factor is calculated: A = 0.00066 (1.0 + 0.00115 T_wb)
3. The saturation vapor pressure is calculated at T_wb: es_wb = e^{[(16.78 T_wb - 116.9)/(T_wb + 237.3)]}
4. The water vapor pressure is calculated: e_d = es_wb - A P (T_db - T_wb)
5. The saturation vapor pressure is calculated at T_db: es_db = e^{[(16.78 T_db - 116.9)/(T_db + 237.3)]}
6. The relative humidity is then calculated: RH = 100 e_d/es_db