Psychrometric Calculator

Air at 30 °C and 60 % relative humidity holds 16.0046 g/kg dry air of water vapour, with a dew point near 21.4 °C.

Dry-bulb temperature (°C):

Relative humidity (%):

Barometric pressure (kPa):

Humidity ratio W =

16.0045544951333 g/kg dry air

Precision

Full answer, then cut to fewer decimals (not rounded):

16.0045544951333 g/kg dry air
16.004554495133 g/kg dry air
16.00455449513 g/kg dry air
16.0045544951 g/kg dry air
16.004554495 g/kg dry air
16.00455449 g/kg dry air
16.0045544 g/kg dry air
16.004554 g/kg dry air
16.00455 g/kg dry air
16.0045 g/kg dry air
16.004 g/kg dry air
16.00 g/kg dry air
16.0 g/kg dry air

Dew point: 21.3900069 °C
Specific enthalpy: 71.10044493 kJ/kg dry air
Specific volume: 0.8808881283 m³/kg dry air
Vapour pressure: 2.541990151 kPa
Saturation pressure: 4.236650251 kPa
Degree of saturation: 58.97067718 %

Step-by-step solution

p_ws = 0.61094 exp(17.625 T/(T + 243.04)) = 4.236650251 kPa; p_v = RH × p_ws = 2.541990151 kPa
W = 0.622 p_v/(P − p_v) = 0.0160045545 kg/kg
h = 1.006T + W(2501 + 1.86T) = 71.10044493 kJ/kg

Psychrometric Formula

W = 0.622 p_v / (P − p_v)

h = 1.006T + W(2501 + 1.86T) kJ/kg dry air; p_v = RH × p_ws

Worked Example

Air at 30 °C and 60 % relative humidity at sea level:

p_ws = 0.61094 exp(17.625 T/(T + 243.04)) = 4.236650251 kPa; p_v = RH × p_ws = 2.541990151 kPa
W = 0.622 p_v/(P − p_v) = 0.0160045545 kg/kg
h = 1.006T + W(2501 + 1.86T) = 71.10044493 kJ/kg

Specific enthalpy: 71.10044493 kJ/kg dry air · Specific volume: 0.8808881283 m³/kg dry air · Vapour pressure: 2.541990151 kPa · Saturation pressure: 4.236650251 kPa · Degree of saturation: 58.97067718 %

GATE tip

In drying, heating air at constant W lowers RH and raises its moisture-holding capacity; follow a horizontal line on the chart.

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Frequently asked questions

What is the difference between relative humidity and humidity ratio?

RH compares vapour pressure with saturation at the same temperature; the humidity ratio is the mass of water per kg of dry air and stays constant when air is heated.

Why does enthalpy include 2501?

It is the latent heat of vaporisation of water at 0 °C in kJ/kg, carried by the vapour in the air.

Sources

The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .

Last reviewed: 2026-10-15. Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.

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APA

Scientific Converters. (2026, October 15). Psychrometric Calculator. Retrieved October 29, 2026, from https://scientificconverters.com/calculators/psychrometric-calculator/

IEEE

Scientific Converters, "Psychrometric Calculator," scientificconverters.com. Accessed: Oct. 29, 2026. [Online]. Available: https://scientificconverters.com/calculators/psychrometric-calculator/