Psychrometric Calculator
Calculate wet bulb temperature, dew point, humidity ratio, enthalpy, and specific volume from dry bulb and relative humidity.
Inputs
ASHRAE 55-2023: comfort zone 30–60% RH; ASHRAE 62.1: no upper limit but condensation risk >70%; typical indoor 40–55%
Results
Wet Bulb Temperature
62.7 °F
Dew Point
55.1 °F
How to Use This Calculator
- Enter Dry Bulb Temperature, Relative Humidity, and Barometric Pressure.
- Review Wet Bulb Temperature (°F) and Dew Point (°F).
- Use Humidity Ratio (gr/lb) and Enthalpy (BTU/lb) to inform your decision.
How the result changes with Dry Bulb Temperature
| Dry Bulb Temperature | Wet Bulb Temperature | Dew Point |
|---|---|---|
| -3 | -4.4 °F | -17 °F |
| 39 | 31.7 °F | 21.9 °F |
| 91 | 76.4 °F | 69.8 °F |
| 133 | 112.5 °F | 108.2 °F |
What each input means
- Dry Bulb Temperature
- Air temperature measured by a standard thermometer, unaffected by moisture.
- Relative Humidity
- Relative humidity as a percentage. Ratio of actual to saturated vapor pressure per ASHRAE Fundamentals Handbook Chapter 1. ASHRAE 55-2023 comfort zone: 30–60% RH at 68–76°F. Below 30% causes static electricity and dry air discomfort.
- Barometric Pressure
- Local barometric pressure. Standard sea level is 29.92 inches Hg. Lower at altitude.
How this is calculated
Worked example, using the default values
- Identify Input ParametersDry Bulb Temperature = 75, Relative Humidity = 50, Barometric Pressure = 29.92 = 3 input(s) provided
- Calculate Wet Bulb TemperatureWet Bulb Temperature62.7 = 62.7
- Calculate Dew PointDew Point55.1 = 55.1
- Calculate Humidity Ratio64.6 = 64.6
- Calculate EnthalpyEnthalpy28.09 = 28.09
Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.
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