Fuel Combustion Energy Calculator
Estimate the energy and calories released when a fuel burns, from its mass and heat of combustion.
How it works
E = mass · heat of combustion · 1 kcal = 4.184 kJ
The energy a fuel gives off is its mass multiplied by its specific heat of combustion (energy per gram). Converting joules to calories uses the thermochemical calorie, 4.184 J, and one food Calorie is one kilocalorie. Higher-energy fuels like gasoline pack roughly three times the energy per gram of dry wood.
Worked example
Burning 10 g of a fuel with a heat of combustion of 40 kJ/g releases 10 × 40 = 400 kJ. That equals 400 / 4.184 ≈ 95.6 kcal.
Sources: Heat of combustion — Wikipedia
Frequently asked questions
What is a typical heat of combustion?
Gasoline is about 46 kJ/g, ethanol about 27 kJ/g, and dry wood around 16 kJ/g. Fats release roughly 37 kJ/g, which is why they are energy-dense.
Are these the same calories as on food labels?
Food Calories (capital C) are kilocalories. The kcal figure here is the same unit, though bomb-calorimeter values overstate metabolizable food energy because the body does not fully oxidize everything.
Does this assume complete combustion?
Yes. Heat of combustion values assume the fuel burns fully to CO₂ and H₂O. Incomplete burning releases less energy and produces soot and carbon monoxide.
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