Heat of Combustion (HHV & LHV) Calculator
Estimate higher and lower heating values from fuel composition or known HHV. See moisture effects, water formation, and energy losses. Get stoichiometric oxygen, air demand, and byproduct masses. Export results as CSV or PDF instantly.
Developed by: Nohman Habib
Example data
| Fuel example | Basis | C% | H% | O% | N% | S% | Ash% | Moisture% | Notes |
|---|---|---|---|---|---|---|---|---|---|
| Typical dry wood | Dry | 50 | 6 | 43 | 0.5 | 0.1 | 0.4 | 10 | Set basis to Dry, then apply moisture 10% |
| Light fuel oil (approx.) | As-received | 86 | 13 | 0.5 | 0.3 | 0.2 | 0 | 0 | Values vary by grade and supplier |
| Coal (illustrative) | As-received | 65 | 4 | 10 | 1 | 1 | 10 | 9 | Make sure totals are near 100% |
Formula
- HHV estimate (Dulong, MJ/kg): HHV = 0.338·C + 1.428·(H − O/8) + 0.095·S (C,H,O,S in mass %).
- Water from hydrogen: m(H₂O) = 9·Hfraction (kg water per kg fuel).
- LHV from HHV: LHV = HHV − hfg·(m(H₂O from H) + moisture), with hfg ≈ 2.442 MJ/kg water.
- Stoichiometric oxygen (kmol/kg): O₂ = n(C) + n(H)/4 + n(S) − n(O)/2.
Note: This calculator provides an engineering estimate. Laboratory bomb calorimetry may differ, especially for complex fuels, high ash, or unusual chemistry.
How to use this calculator
- Select a calculation method: ultimate analysis estimation, HHV→LHV, or LHV→HHV.
- If using ultimate analysis, enter C, H, O, N, S, ash, and moisture on your chosen basis.
- Choose “As-received” if your inputs already include moisture. Choose “Dry” if moisture is separate and you want it applied afterward.
- Click Calculate to see HHV, LHV, water correction, and (for ultimate analysis) stoichiometric oxygen, air, and byproducts.
- Use Download CSV or Download PDF to export the computed results and steps.
FAQs
1) What is the difference between HHV and LHV?
HHV assumes the water produced during combustion condenses, recovering its latent heat. LHV assumes water stays as vapor, so that latent heat is not recovered and the reported value is lower.
2) Why does moisture reduce the LHV?
Moisture must be heated and evaporated during combustion. The energy used to vaporize water is not available as useful heat, so LHV decreases as moisture increases.
3) Why is hydrogen important in LHV correction?
Hydrogen in the fuel forms water when burned. That water is typically treated as vapor for LHV, so the latent heat tied to water formation is subtracted from HHV.
4) Is the HHV computed here exact?
No. The Dulong method is an estimate based on elemental composition and is commonly used for quick engineering calculations. For exact values, use measured calorimetry data for your specific fuel.
5) What does “stoichiometric air” mean?
Stoichiometric air is the theoretical minimum air required for complete combustion (no leftover fuel and no leftover oxygen), based on the fuel’s elemental makeup.
6) What should I enter if my analysis is on a dry basis?
Choose the Dry basis option, enter C, H, O, N, S, and ash so they total near 100%, then enter the moisture percentage you want applied to convert results to an as-received basis.