Introduction & principle
Vapor pressure e=es(T)RH/100; mixing ratio r=0.62198e/(P−e); specific humidity q=r/(1+r). Results multiply kg/kg by 1000 for g/kg. Use station pressure, not sea-level pressure. Magnus saturation is over liquid water.
All tools
Meteorological Calculation
Mixing Ratio & Specific Humidity
Calculate water-vapor mass relative to dry air and to total moist air.
Use this tool
Preparing interactive controls…
Worked example
At 20°C, RH50% and 1000 hPa, r is about 7.34 g/kg dry air and q about 7.29 g/kg moist air. RH 0 produces both zero.
Detailed usage guide
- 1Enter temperature −45–60°C and RH 0–100%.
- 2Enter station pressure 100–1100 hPa; vapor pressure must remain below total pressure.
- 3Compare the dry-air denominator of mixing ratio with the total-air denominator of specific humidity.
Common problems & FAQ
Why do the two mass ratios differ?
Mixing ratio divides vapor mass by dry-air mass. Specific humidity divides it by total moist-air mass, so q=r/(1+r) and is slightly smaller.
Methods & references
Method reviewed November 4, 2026. These tools support learning and recording, not safety-critical decisions.