Heat of Combustion Calculator
Pick one of 32 fuels or type a formula and its ΔH°f to get the heat of combustion in kJ/mol, kJ/g, MJ/kg, kcal and BTU/lb, the ΔcU, and the heat from any mass or moles.
ΔH°comb = Σ ΔH°f(products) − Σ ΔH°f(reactants).
Use the Heat of Combustion Calculator
Combustion Parameters
Fills the atom counts below. C, H, O and N only.
Auto: C = 12.011, H = 1.008, O = 15.999, N = 14.007.
Unit Relationships & Scope
- 1 kJ/g = 1 MJ/kg = 429.92 BTU/lb = 0.2390 kcal/g. 1 kWh = 3.6 MJ.
- HHV − LHV: 44.0 kJ per mol of H₂O formed (−241.8 − (−285.8)). Fuels without hydrogen have identical HHV and LHV.
- ΔcU = ΔcH − Δn(gas)·RT, RT = 2.479 kJ/mol at 298.15 K; solids and liquids count as zero gas.
- Scope: complete combustion of CₓHᵧOᵤN𝑤 to CO₂(g), H₂O and N₂(g). Compounds that need no external O₂ are excluded.
Select a fuel and click Calculate to see results.
Balanced Combustion Equation
Molar Enthalpy
Specific Energy
Energy Density
- Other units
- Bomb calorimeter ΔcU (constant volume)
- Heat released by the amount entered
Hess's Law Calculation Breakdown
Heat of Combustion Table: 32 Fuels and Compounds
Standard heats of combustion at 25 °C computed with Hess's law from the ΔH°f values shown. HHV = water liquid, LHV = water vapor; the heat released is the negative of ΔH°comb.
| Substance | Formula | ΔH°f (kJ/mol) | ΔH°comb (kJ/mol) | HHV (MJ/kg) | LHV (MJ/kg) | HHV (BTU/lb) |
|---|---|---|---|---|---|---|
| Hydrogen | H₂(g) | 0.0 | -285.8 | 141.77 | 119.94 | 60,948 |
| Carbon monoxide | CO(g) | -110.5 | -283.0 | 10.10 | 10.10 | 4,344 |
| Methane | CH₄(g) | -74.8 | -890.3 | 55.49 | 50.01 | 23,858 |
| Ethane | C₂H₆(g) | -84.0 | -1,560.4 | 51.89 | 47.50 | 22,310 |
| Propane | C₃H₈(g) | -104.7 | -2,219.0 | 50.32 | 46.33 | 21,634 |
| n-Butane | C₄H₁₀(g) | -125.6 | -2,877.4 | 49.50 | 45.72 | 21,283 |
| Ethylene | C₂H₄(g) | 52.4 | -1,411.0 | 50.30 | 47.16 | 21,623 |
| Propene | C₃H₆(g) | 20.0 | -2,057.9 | 48.90 | 45.77 | 21,025 |
| Acetylene | C₂H₂(g) | 227.4 | -1,300.2 | 49.93 | 48.24 | 21,468 |
| Dimethyl ether | C₂H₆O(g) | -184.1 | -1,460.3 | 31.70 | 28.83 | 13,628 |
| n-Pentane | C₅H₁₂(l) | -173.5 | -3,508.8 | 48.63 | 44.97 | 20,908 |
| n-Hexane | C₆H₁₄(l) | -198.7 | -4,162.9 | 48.31 | 44.73 | 20,768 |
| n-Heptane | C₇H₁₆(l) | -224.2 | -4,816.7 | 48.07 | 44.56 | 20,666 |
| n-Octane | C₈H₁₈(l) | -250.1 | -5,470.1 | 47.89 | 44.42 | 20,587 |
| Isooctane (2,2,4-trimethylpentane) | C₈H₁₈(l) | -259.2 | -5,461.0 | 47.81 | 44.34 | 20,553 |
| Cyclohexane | C₆H₁₂(l) | -156.4 | -3,919.4 | 46.57 | 43.43 | 20,021 |
| Benzene | C₆H₆(l) | 49.1 | -3,267.5 | 41.83 | 40.14 | 17,984 |
| Toluene | C₇H₈(l) | 12.4 | -3,910.1 | 42.44 | 40.53 | 18,244 |
| Methanol | CH₄O(l) | -238.7 | -726.4 | 22.67 | 19.92 | 9,746 |
| Ethanol | C₂H₆O(l) | -277.7 | -1,366.7 | 29.67 | 26.80 | 12,754 |
| 1-Propanol | C₃H₈O(l) | -302.6 | -2,021.1 | 33.63 | 30.70 | 14,459 |
| 2-Propanol (isopropanol) | C₃H₈O(l) | -318.1 | -2,005.6 | 33.37 | 30.44 | 14,348 |
| 1-Butanol | C₄H₁₀O(l) | -327.3 | -2,675.7 | 36.10 | 33.13 | 15,519 |
| Acetone | C₃H₆O(l) | -248.4 | -1,789.5 | 30.81 | 28.54 | 13,246 |
| Acetic acid | C₂H₄O₂(l) | -484.3 | -874.3 | 14.56 | 13.09 | 6,259 |
| Glycerol | C₃H₈O₃(l) | -668.5 | -1,655.2 | 17.97 | 16.06 | 7,727 |
| Carbon (graphite) | C(s) | 0.0 | -393.5 | 32.76 | 32.76 | 14,085 |
| Glucose | C₆H₁₂O₆(s) | -1,273.3 | -2,802.5 | 15.56 | 14.09 | 6,688 |
| Sucrose | C₁₂H₂₂O₁₁(s) | -2,222.1 | -5,643.7 | 16.49 | 15.07 | 7,088 |
| Naphthalene | C₁₀H₈(s) | 78.5 | -5,156.7 | 40.23 | 38.86 | 17,297 |
| Benzoic acid (calorimeter standard) | C₇H₆O₂(s) | -385.2 | -3,226.7 | 26.42 | 25.34 | 11,359 |
| Urea | CH₄N₂O(s) | -333.1 | -632.0 | 10.52 | 9.06 | 4,524 |
ΔH°f values: NIST Chemistry WebBook (SRD 69) and the CRC Handbook of Chemistry and Physics; CO₂(g) −393.5, H₂O(l) −285.8, H₂O(g) −241.8 kJ/mol. The computed ΔH°comb values agree with NIST measured heats of combustion to within about 1 kJ/mol. Commercial fuels (gasoline, diesel, natural gas, wood) are mixtures whose heating values are measured, not calculated.
Worked Example: Ethanol, HHV, LHV and ΔcU
- Balance: C₂H₅OH(l) + 3 O₂ → 2 CO₂(g) + 3 H₂O(l). O₂ = 2 + 6/4 − 1/2 = 3.
- Products: 2(−393.5) + 3(−285.8) = −1,644.4 kJ. Reactants: −277.7 + 3(0) = −277.7 kJ.
- ΔH°comb = −1,644.4 − (−277.7) = −1,366.7 kJ/mol; ÷ 46.069 g/mol = 29.67 kJ/g = 29.67 MJ/kg (HHV).
- LHV: three moles of water stay as vapor, so add 3 × 44.0 = 132.0 kJ: −1,234.7 kJ/mol = 26.80 MJ/kg.
- ΔcU: gases go from 3 mol O₂ to 2 mol CO₂, Δn = −1, so ΔcU = −1,366.7 + 2.479 = −1,364.2 kJ/mol.
Quick answer
ΔH°comb = Σ ΔH°f(products) − Σ ΔH°f(reactants). To convert kJ/mol to kJ/g, divide by the molar mass in g/mol, and kJ/g equals MJ/kg. Values below are higher heating values with liquid water, from this tool's NIST formation enthalpies.
Examples
| Fuel | ΔH°comb (kJ/mol) | Heat released (MJ/kg) |
|---|---|---|
| Methane CH4 | −890.3 | 55.49 |
| Ethylene C2H4 | −1,411.0 | 50.30 |
| Propane C3H8 | −2,219.0 | 50.32 |
| Butane C4H10 | −2,877.4 | 49.50 |
| Methanol CH3OH | −726.4 | 22.67 |
| Ethanol C2H5OH | −1,366.7 | 29.67 |
Pick a fuel or type a formula like C8H18 to get the balanced equation, HHV or LHV, ΔcU and the heat from your own amount.
Summary
The Heat of Combustion Calculator determines the standard enthalpy of combustion (ΔH°comb) of fuels and organic compounds with Hess's law: ΔH°comb = Σ ΔH°f(products) − Σ ΔH°f(reactants), with products CO₂(g), H₂O and N₂(g). Choose the higher heating value (HHV, liquid water) or lower heating value (LHV, water vapor), pick one of 32 preset fuels or type any CₓHᵧOᵤN𝑤 formula, and read the result per mole, per gram, per kilogram, in kcal and BTU/lb, as the constant-volume ΔcU measured in a bomb calorimeter, and as the total heat from any amount of fuel. A server-rendered table lists HHV and LHV for every preset.
How it works
- Choose a preset fuel, or type a molecular formula (C, H, O and N, e.g. C8H18 or CH3CH2OH) with its standard enthalpy of formation ΔH°f and physical state.
- Select Higher Heating Value (HHV, H₂O liquid) or Lower Heating Value (LHV, H₂O gas).
- The calculator balances CₓHᵧOᵤN𝑤 + (x + y/4 − z/2) O₂ → x CO₂ + y/2 H₂O + w/2 N₂.
- It evaluates ΔH°comb = Σ ν_p ΔH°f(products) − Σ ν_r ΔH°f(reactants) with CO₂(g) −393.5, H₂O(l) −285.8 and H₂O(g) −241.8 kJ/mol.
- ΔcU = ΔcH − Δn(gas)·RT gives the constant-volume value a bomb calorimeter measures (RT = 2.479 kJ/mol at 298.15 K).
- Enter an amount in g, kg, lb or mol to get the total heat in kJ, MJ, kWh, kcal and BTU.
Use cases
- Compare higher (gross) and lower (net) heating values for hydrocarbons, alcohols and biofuels.
- Solve thermochemistry problems in general, physical, and organic chemistry coursework.
- Find how much heat burning a given mass of propane, ethanol or octane releases.
- Cross-check bomb calorimetry data (ΔcU) against theoretical values, e.g. benzoic acid calibration.
- Convert heating values between kJ/mol, MJ/kg, kcal/g and BTU/lb.