Steam Quality (Dryness Fraction) Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 26, 2026Steam Quality (Dryness Fraction) Calculator
Wet steam is not simply "steam" - it is a mixture of vapor and entrained liquid droplets, and dryness fraction quantifies exactly what proportion is actually vapor.
The Formula
x = (h - hf) / hfg
Worked Example
Actual enthalpy 2,400 kJ/kg, saturated liquid enthalpy 762 kJ/kg, latent heat 2,015 kJ/kg: x = (2400-762)/2015 ≈ 0.813 - about 81% vapor by mass.
Frequently Asked Questions
Why does steam quality matter for turbines?
Liquid droplets in low-quality steam cause erosion on turbine blades over time, which is why steam turbine designs specify a minimum acceptable quality (often around 0.88-0.90) at the low-pressure turbine exit.
What does a quality outside 0-1 mean?
A result below 0 or above 1 indicates the steam is actually subcooled liquid or superheated vapor rather than a genuine two-phase wet mixture, and the dryness fraction concept does not apply.