Physics

Instant, private, and free

Absolute Humidity Calculator.

Calculate water-vapour mass density from vapour pressure and absolute temperature using the ideal-gas relation.

On-device calculationNo signup
01

Set your values

Results update as you type.

Absolute humidity: 0.00887 kg/m³

Absolute humidity

0.008870kg/m³

Results update automatically as you type.

Use Cases

HVAC and environmental monitoring

Determine the moisture content in air for climate control, drying processes, or comfort assessments.

Example: Check absolute humidity in a greenhouse with vapour pressure 2000 Pa at 300 K.

Meteorology and weather analysis

Analyse atmospheric moisture levels for weather prediction or climate studies.

Example: Compute absolute humidity from a weather station's vapour pressure and temperature data.

Frequently Asked Questions

What is absolute humidity?
Absolute humidity is the mass of water vapour per unit volume of air, expressed in grams per cubic meter (g/m³). It is calculated using the ideal-gas relation from the water-vapour pressure and absolute temperature.
How do I use this calculator?
Enter the water-vapour pressure in Pascals (Pa) and the absolute temperature in Kelvin (K). The calculator then applies the ideal-gas relation to compute the absolute humidity in g/m³.
Why is absolute temperature in Kelvin?
The ideal-gas relation requires temperature in Kelvin, which is an absolute scale starting at absolute zero. Using Celsius or Fahrenheit would give incorrect results because they are relative scales.

Tips & Common Mistakes

Tips

  • Ensure the water-vapour pressure is in Pascals (Pa). If you have it in hPa, multiply by 100.
  • Convert temperature to Kelvin by adding 273.15 to Celsius.
  • Use the ideal-gas constant for water vapour (461.5 J/(kg·K)) for accurate results.
  • Double-check your inputs for consistency; small errors in pressure or temperature can affect the result.

Common Mistakes to Avoid

  • Using Celsius or Fahrenheit instead of Kelvin for temperature.
  • Entering vapour pressure in hPa or mmHg without converting to Pascals.
  • Confusing absolute humidity with relative humidity; this calculator only computes absolute humidity.

Last updated: August 13, 2026