HHV to LHV Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026Two ways of measuring a fuel's heat content
Higher heating value (HHV) and lower heating value (LHV) differ by exactly one thing: whether the latent heat of water vapor formed during combustion is counted. HHV includes it (assuming the water condenses back to liquid), while LHV excludes it, matching what most real combustion equipment actually recovers.
Worked example
For methane (HHV 55,500 kJ/kg, 25% hydrogen by mass):
Water Formed = 9 x 0.25 = 2.25 kg water per kg fuel
LHV = 55500 - (2.25 x 2260) = 50,415 kJ/kg
This result closely matches methane's actual published LHV of roughly 50,000 kJ/kg, confirming the formula. The factor of 9 comes directly from water's molecular weight relative to hydrogen (H2O = 18, H2 = 2, ratio = 9) - every kilogram of hydrogen burned produces exactly 9 kilograms of water.
Boiler and furnace efficiency ratings in North America are typically based on HHV, while many European and industrial gas turbine specifications use LHV - always check which basis a quoted efficiency figure uses before comparing equipment across different specification standards.