Heat of Combustion Calculator
Calculate the heat released when burning fuels.
Choose from methane, ethanol, propane, octane, hydrogen, or enter a custom combustion enthalpy.
Heat of Combustion
The heat of combustion (ΔH_combustion) is the enthalpy change when one mole of a substance burns completely in excess oxygen under standard conditions (25°C, 1 atm).
Formula:
q = |ΔH_c| × n
where n = moles of fuel burned.
Standard heats of combustion (higher heating values, liquid water product):
| Fuel | Molar Mass (g/mol) | ΔH_c (kJ/mol) | Energy/g (kJ/g) |
|---|---|---|---|
| Hydrogen (H₂) | 2.016 | −285.8 | −141.8 |
| Methane (CH₄) | 16.04 | −890.4 | −55.5 |
| Ethanol (C₂H₅OH) | 46.07 | −1366.8 | −29.7 |
| Propane (C₃H₈) | 44.10 | −2220.0 | −50.3 |
| Butane (C₄H₁₀) | 58.12 | −2877.5 | −49.5 |
| Octane (C₈H₁₈) | 114.2 | −5471.0 | −47.9 |
| Carbon (graphite) | 12.01 | −393.5 | −32.8 |
| Glucose (C₆H₁₂O₆) | 180.2 | −2803.0 | −15.6 |
Higher vs Lower Heating Value:
- Higher (HHV): water product is liquid — more heat released
- Lower (LHV): water product is gas — accounts for vaporization energy
Real-world energy comparison:
- 1 kg methane ≈ 55.5 MJ (LNG fuel)
- 1 kg gasoline (octane equivalent) ≈ 47.9 MJ
- 1 kg wood (dry) ≈ 15-18 MJ
- 1 kg TNT (explosive equivalent) ≈ 4.6 MJ
- 1 kg hydrogen ≈ 141.8 MJ (highest energy density by mass of any fuel)