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Dew Point, Wet Bulb & Psychrometrics Calculator

Estimates at fixed 101.325 kPa. Input range: 0–50°C, RH 5–99%. Not for compressed-air pressure dew point, altitude correction, frost point, or safety decisions.

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Estimates at fixed 101.325 kPa. Input range: 0–50°C, RH 5–99%. Not for compressed-air pressure dew point, altitude correction, frost point, or safety decisions.

Inputs are processed in this browser without upload or storage.

Magnus uses liquid-water saturation pressure and its inverse for dew point. Stull (2011) estimates wet bulb at sea level. Humidity ratio and enthalpy use the displayed moist-air equations.

Only estimates: Stull has empirical error and may not preserve exact thermodynamic relationships. Below-zero dew point remains a liquid-water estimate, not frost point. No pressure input or compressed-air calculation is supported.

T: °C; RH: %; P = 101.325 kPa
γ = ln(RH/100) + 17.625T/(243.04 + T); Td = 243.04γ/(17.625 − γ)
es = 0.61094 exp(17.625T/(243.04 + T)); e = es × RH/100 (kPa)
W = 0.621945e/(P − e) (kg/kg); h = 1.006T + W(2501 + 1.86T) (kJ/kg)
Tw = T atan(0.151977√(RH + 8.313659)) + atan(T + RH) − atan(RH − 1.676331) + 0.00391838 RH^1.5 atan(0.023101RH) − 4.686035

NOAA: Magnus · UCAR: Stull (2011) · PsychroLib / ASHRAE

A QUICK WALKTHROUGH

How to use this tool

  1. Enter dry-bulb temperature and choose °C or °F.
  2. Enter relative humidity from 5 to 99%.
  3. Review estimates at standard sea-level pressure.

Dew Point, Wet Bulb & Psychrometrics Calculator

Magnus uses liquid-water saturation pressure and its inverse for dew point. Stull (2011) estimates wet bulb at sea level. Humidity ratio and enthalpy use the displayed moist-air equations.

Can I calculate pressure dew point or altitude effects?

Only estimates: Stull has empirical error and may not preserve exact thermodynamic relationships. Below-zero dew point remains a liquid-water estimate, not frost point. No pressure input or compressed-air calculation is supported.

GOOD TO KNOW

Common questions

Can I calculate pressure dew point or altitude effects?

No. Pressure is fixed at 101.325 kPa. Use a pressure-aware validated model for those conditions.

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