Dew Point & Psychrometrics Calculator
Enter dry-bulb temperature, relative humidity, and pressure. Calculates saturation vapor pressure, vapor/air partial pressures, humidity ratio, dry-air density, dew point, and wet-bulb. Export to Excel with live formulas.
Saturation vapor pressure (at dry-bulb)
– Pa
Partial pressure of water vapor
– Pa
Partial pressure of dry air
– Pa
Humidity ratio
– kg/kgdry air
Dry air density
– kg/m³
Dew point temperature
– °C
Wet-bulb temperature (Stull)
– °C
Formula & unit notes
- Saturation vapor pressure (Buck 1981; over water):
e_s(T) = 611.21 · EXP((18.678 − T/234.5) · (T/(257.14 + T)))[Pa], T in °C. - Actual vapor pressure:
p_v = (RH/100) · e_s. - Dry-air partial pressure:
p_da = p_total − p_v. - Humidity ratio:
w = 0.621945 · p_v / p_da(kg/kg dry air). - Dry-air density:
ρ_da = p_da / (R_da · (T+273.15)),R_da = 287.058J·kg⁻¹·K⁻¹. - Dew point (inverse Buck/Magnus):
T_dp = (257.14·LN(p_v/611.21)) / (18.678 − LN(p_v/611.21))[°C]. - Wet-bulb (approximation): Stull (2011).