Inputs

Temperature (°F)
Relative Humidity (%)
Dew Point (°F)
Input Pair
Temperature + Dew Point
Temperature + Relative Humidity
Dew Point + Relative Humidity
Temperature Units
°F
°C

Outputs

Saturation Vapor Pressure (es)
0.000 kPa
Actual Vapor Pressure (ea)
0.000 kPa
Relative Humidity
0.0 %
Wet-Bulb Temperature
0.0 °F
Dew Point
0.0 °F

Psychrometric Snapshot

Saturation vapor pressure vs. temperature. The curve is the saturation curve; the horizontal line is the actual vapor pressure. Vertical markers show temperature, dew point, and wet bulb.

Humidity Lookup Table

Enter desired relative humidity (%) to highlight air temperature and dew point. Top row shows temperature in °F (with °C beneath).
The desired % is green; ±5% is amber.
Dew Point (°F) °C kPa Temperature (°F)
585960616263646566676869707172737475
14.415.015.616.116.717.217.818.318.919.420.020.621.121.722.222.823.323.9

Equations Used

Unit conversion: T(°C) = (T(°F) − 32) × 5/9;   T(°F) = T(°C) × 9/5 + 32
Saturation VP (Tetens, over water): es(Tc) = 0.61078 · exp( (17.27·Tc) / (Tc + 237.3) )  [kPa]
Inverse Tetens (T from e): Tc = 237.3 · ln(e/0.61078) / (17.27 − ln(e/0.61078))
Actual VP from RH & T: ea = (RH / 100) · es(Tc)  [kPa]
RH from T & ea: RH (%) = 100 · ea / es(Tc)
Dew point from ea: Td,c = InverseTetens(ea)
Wet-bulb (Stull 2011, °C): Tw ≈ T · atan(0.151977√(RH + 8.313659)) + atan(T + RH) − atan(RH − 1.676331) + 0.00391838·RH3/2·atan(0.023101·RH) − 4.686035
Notes: T, Td, Tw are in °C inside the formulas; RH in %; vapor pressures in kPa.