Psychrometric Calculator & Chart
Input Data
Enter your project data
Sets the atmospheric pressure (sea level = 101.325 kPa(a)).
Optional: mass flow, moisture flow and sensible heating / cooling power (kW/K).
Calculation Results
Calculated instantly from your inputs
Psychrometrics
Psychrometrics describes moist air: a mixture of dry air and water vapour. Two independent properties (for example dry bulb and relative humidity) fix the state at a given pressure; all other properties follow. HVAC engineers use them to size coils (enthalpy difference), to check condensation (dew point), for cooling towers and evaporative coolers (wet bulb) and for humidification (humidity ratio).
Key Points:
- Dew point: surfaces colder than this get condensation
- Wet bulb: the lowest temperature evaporative cooling can reach; design value for cooling towers
- Coil load: Q = ṁ · (h₁ − h₂) with the enthalpies of the entering and leaving air
- Humidity ratio stays constant in sensible heating / cooling (horizontal line on the chart)
- Altitude matters: at 1500 m the air pressure is about 84 kPa - humidity ratio and density change
- Comfort zone: about 20-26 °C and 30-60 % relative humidity
Calculation Steps:
- Enter all required parameters
- Click "Update Calculation"
- Review results and analysis
Formula Variables:
W
Humidity ratio
(kg/kg dry air)
pw
Water vapour partial pressure
(Pa)
pws
Saturation vapour pressure
(Pa)
φ
Relative humidity
(%)
h
Specific enthalpy of moist air
(kJ/kg dry air)
p
Atmospheric pressure
(Pa)