# Psychrometric Properties (Humidity Ratio / Enthalpy / RH) Compute the full set of moist-air (psychrometric) state properties from dry-bulb temperature plus one humidity input (relative humidity φ, wet-bulb temperature, dew-point temperature, or humidity ratio W). Returns humidity ratio W (kg/kg and g/kg), relative humidity φ (%), dew-point, wet-bulb, enthalpy h (kJ/kg dry air), specific volume v (m³/kg dry air), partial vapour pressure P_w, and saturation pressure P_ws. Uses the Magnus saturation-pressure fit; wet-bulb is solved iteratively from the thermodynamic psychrometric equation. Default standard atmosphere 101.325 kPa (adjustable). Temperature in °C/K/°F; all reported temperatures are in °C. > Canonical page: https://elysiatools.com/en/tools/psychrometric-properties - **Category:** Math & Numbers - **Keywords:** psychrometric, psychrometrics, humidity ratio, relative humidity, enthalpy, dew point, wet bulb, dry bulb, specific volume, moist air, Magnus, ASHRAE ## Overview Calculate the complete psychrometric state of moist air from dry-bulb temperature and one humidity input: relative humidity, wet-bulb temperature, dew point, humidity ratio, enthalpy, specific volume, vapour pressure, and saturation pressure. ## Inputs - **Dry-bulb Temperature** (number): Dry-bulb (ambient air) temperature, in the selected Temperature Unit. - **Temperature Unit** (select) - **Known Humidity Input** (select): Which humidity parameter the Humidity Input Value represents. - **Humidity Input Value** (number): Value of the selected Known Humidity Input. RH in % (0–100); wet-bulb / dew-point in the selected Temperature Unit; humidity ratio in the selected Humidity Ratio Unit. - **Humidity Ratio Unit** (select) - **Atmospheric Pressure** (number): Total atmospheric pressure P, in the selected Pressure Unit. Default 101.325 kPa (sea level). - **Pressure Unit** (select) - **Decimal Places** (number) ## When to use - Convert a dry-bulb and relative-humidity reading into humidity ratio, dew point, wet-bulb temperature, and enthalpy. - Derive relative humidity and other moist-air properties from a known humidity ratio. - Check psychrometric conditions at standard or site-specific atmospheric pressure. ## How it works - Enter the dry-bulb temperature and select °C, K, or °F. - Choose one known humidity input: relative humidity, wet-bulb temperature, dew-point temperature, or humidity ratio. - Enter atmospheric pressure, or use the default 101.325 kPa, and select the humidity-ratio and pressure units. - The calculator applies the Magnus saturation-pressure fit and iteratively solves wet-bulb temperature, returning the full state as JSON. ## Use cases - HVAC design checks using temperature, humidity, pressure, enthalpy, and specific volume. - Indoor-air and environmental measurements that require dew-point or wet-bulb calculations. - Engineering and laboratory calculations involving moist-air mass and energy properties. ## Frequently asked questions ### What inputs are required? Enter a dry-bulb temperature and one humidity value. The humidity value can be relative humidity, wet-bulb temperature, dew-point temperature, or humidity ratio. ### Which temperature units are supported? Dry-bulb and humidity temperatures can be entered in °C, K, or °F. Reported temperatures are returned in °C. ### What atmospheric pressure is used? The default pressure is 101.325 kPa. You can replace it with a custom value in kPa or hPa. ### What properties does the calculator return? Results include humidity ratio, relative humidity, dew point, wet bulb, enthalpy, specific volume, partial vapour pressure, and saturation pressure. ### Can humidity ratio be entered in g/kg? Yes. 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