Psychrometric Calculator
Compute dew point, vapor pressure, humidity ratio, and specific humidity
How to Use This Calculator
Enter Dry-bulb Temperature
Provide ambient air temperature in °C.
Enter Pressure
Provide station pressure in hPa.
Enter Relative Humidity
Provide RH as a percentage (0–100%).
Calculate
Review dew point, vapor pressure, and humidity ratios.
Formula
e_s(T) = 6.112 · exp((17.67·T)/(T+243.5)) [hPa]
e = RH/100 · e_s(T), p_d = p − e
w = 0.622 · e / p_d, q = w / (1 + w)
Td via Magnus: γ = ln(RH/100) + aT/(b+T), Td = bγ/(a−γ)
Constants: a=17.27, b=237.7 °C
About Psychrometrics
Psychrometrics deals with the thermodynamic properties of moist air. These parameters are used in HVAC design, meteorology, and comfort analysis.
Frequently Asked Questions
What is the difference between mixing ratio and specific humidity?
Mixing ratio is per mass of dry air; specific humidity is per mass of moist air. Values are similar at typical conditions.
Can I compute wet-bulb temperature here?
This simple tool does not compute wet-bulb; we can extend it if needed.