Absolute Humidity Calculator
Find absolute humidity from temperature and relative humidity.
Absolute humidity is the actual mass of water vapour per cubic metre of air.
How the Math Works
The formula calculates absolute humidity by first determining the saturation vapor pressure using the Magnus equation: 6.112·e^(17.67T/(T+243.5)), where T is temperature in Celsius. This value represents the maximum water vapor air can hold at that temperature. Multiplying by relative humidity (RH) gives the actual vapor pressure. The 2.1674 constant converts vapor pressure (in hPa) to grams per cubic meter, while dividing by (273.15+T) adjusts for temperature in Kelvin, ensuring accurate mass-to-volume conversion.
Practical Applications
To apply this calculation, input your local temperature and relative humidity into the calculator. For instance, if the temperature is 25°C and RH is 60%, the formula computes the exact mass of water vapor in the air. This is critical for industries like agriculture, where precise humidity levels optimize crop yields, or HVAC engineering, where it helps design systems for efficient air conditioning and dehumidification.
Day-to-Day Use
Understanding absolute humidity helps in daily comfort and health. High absolute humidity can make air feel stickier, affecting physical activity or sleep quality, while low levels may cause dryness or respiratory irritation. It also aids in practical tasks like choosing appropriate clothing, managing indoor plant health, or adjusting exercise routines during humid days to prevent overheating.
Worked example
25 °C at 60% RH → about 13.8 g/m³.
FAQ
Absolute vs relative humidity?
Absolute is a fixed mass per volume; relative is a percentage of the maximum possible.