Heat of Combustion Calculator

The Heat of Combustion Calculator measures how much energy is released when a fuel burns completely — useful for comparing fuels, sizing combustion systems, or checking energy output in engineering and chemistry applications. Select your fuel type (methane, propane, gasoline, and more, or enter a custom fuel), enter your fuel amount and unit, and adjust the thermodynamic and stoichiometric inputs to get the Higher Heating Value (HHV) in MJ. Secondary outputs include Lower Heating Value (Total), Water Vaporization Energy, and Specific HHV.

MJ/kg

For custom fuel only. Predefined fuels use standard values.

MJ/kg

Heat required to vaporize water at standard conditions

Number of water molecules produced per fuel molecule

Results

Higher Heating Value (HHV)

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Lower Heating Value (Total)

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Water Vaporization Energy

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Specific HHV

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Frequently Asked Questions

What is heat of combustion?

Heat of combustion is the amount of energy released when a fuel undergoes complete combustion with oxygen. It's measured as the higher heating value (HHV) which includes the energy from condensing water vapor produced during combustion.

How do you calculate heat of combustion?

Heat of combustion is calculated using the formula: HHV = LHV + (Heat of Vaporization × Water to Fuel Molar Ratio × Fuel Amount). This accounts for both the lower heating value and the energy released from condensing water vapor.

What is the difference between LHV and HHV?

Lower Heating Value (LHV) measures energy released without condensing water vapor, while Higher Heating Value (HHV) includes the additional energy from condensing the water vapor produced during combustion. HHV is always higher than LHV.

Why is heat of vaporization important in combustion calculations?

Heat of vaporization is crucial because combustion produces water vapor. When this vapor condenses, it releases additional energy. Including this energy gives the true total heat released during combustion (HHV).

What is the heat of vaporization of water?

The heat of vaporization of water at standard conditions is approximately 2.26 MJ/kg or 970 BTU/lb. This is the energy required to convert liquid water to vapor, or released when vapor condenses to liquid.

Can I use this calculator for any type of fuel?

Yes, the calculator includes predefined values for common fuels like hydrogen, methane, propane, and gasoline. You can also use the custom option to input values for any other fuel by providing its LHV and stoichiometric data.

What units can I use for fuel amount?

The calculator supports multiple units including kilograms, pounds, grams, and standard cubic feet. Results are automatically converted and displayed in megajoules (MJ) for energy values.