Environmental & Climate

Psychrometric Chart

Air property calculations for HVAC and dehumidification workflows.

Available on Solo — start free

The Psychrometric Chart needs a Solo plan or higher. Create a free account to get started, then upgrade when you need it.

Start free Already have an account? Sign in

What it does

A psychrometric calculator that works out moist-air properties from dry bulb temperature plus one other property at a given barometric pressure. It also checks the result against crop-type temperature, humidity and VPD ranges.

When to use it

Use it to find wet bulb, dew point, humidity ratio, enthalpy, specific volume, density and VPD for a room or outdoor condition. Pressure can be corrected for site elevation.

How it calculates

Saturation vapor pressure from the Magnus equation: es = 0.6108·exp(17.27·T ÷ (T + 237.3))
Wet bulb is solved by Newton-Raphson iteration of e = es(Tw) − 0.00066 × P × (Tdb − Tw).
Humidity ratio = 0.622·e ÷ (P − e). Specific volume = 0.287·T(K)·(1 + 1.608·W) ÷ P. Enthalpy = 1.006·T + W·(2501 + 1.86·T).
Barometric pressure from elevation: 101.325 × (1 − 0.0065 × h ÷ 288.15)^5.255

What you enter

Dry Bulb Temperature(°C)
Relative Humidity (%), Wet Bulb Temperature (°C), Dew Point (°C) or Absolute Humidity (g/kg)
Crop Type
Elevation(m)
Barometric Pressure(kPa)
Precision(decimal places)
US ZIP code

What you get

Wet Bulb Temp(°C)
Dew Point(°C)
Relative Humidity(%)
Absolute Humidity(g/kg)
Specific Volume(m³/kg)
Enthalpy(kJ/kg)
Density(kg/m³)
VPD(kPa)

Related calculators

All calculators