Psychrometric chart
Explore air properties, compare two states and calculate air mixing.
Air state
Click the chart to set the active point. Use the inputs for precise keyboard entry.
Air-state chart
101.325 kPaA → B process & air mixing
Dry-air mass basisCalculation method & reading the chart ＋
The horizontal axis is dry-bulb temperature; the vertical axis is humidity ratio per kg of dry air. The boundary curve is 100% RH saturation. Toggle relative humidity, enthalpy, wet-bulb and specific-volume lines. Chart temperature range: −20 to 60 °C; the humidity axis expands to include valid points.
Saturation vapor pressure follows Hyland–Wexler/ASHRAE. W = 0.621945·Pv/(P−Pv); h = 1.006·T + W(2501 + 1.86·T). Wet bulb and dew point are solved iteratively. Below 0 °C, saturation and dew point use equilibrium over ice (frost point).
Total heat A → B = ṁda(hB−hA); water added/removed = ṁda(WB−WA). Mixing balances enthalpy and water vapor using dry-air mass fractions. Supersaturated mixtures are flagged; condensation or fog separation is not modeled. RH = 0 has no finite dew point.
ASHRAE — Psychrometrics