Wobbe Index Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 26, 2026Wobbe Index Calculator
Gas grid operators need a single number that predicts whether two different fuel gases will behave the same way through the same burner - that number is the Wobbe Index, the standard industry measure of fuel gas interchangeability.
The Formula
WI = HV / √SG
Worked Example
A gas with 38 MJ/m³ heating value and 0.6 specific gravity: WI = 38 / √0.6 ≈ 49.06 MJ/m³ - squarely within the typical pipeline natural gas Wobbe Index range.
How to Use This Calculator
- Enter the gas's heating value.
- Enter its specific gravity relative to air.
Two gases sharing the same Wobbe Index deliver approximately the same heat output through the same burner orifice at the same supply pressure, even if their individual heating values and densities differ substantially - which is exactly why grid operators set Wobbe Index limits rather than heating value limits alone when blending gases.