Fuel Heating Value Calculator

Work out fuel heating value instantly with clear inputs, formula shown and shareable results.

About Fuel Heating Value Calculator

The higher heating value assumes the water produced condenses and gives back its latent heat; the lower heating value assumes it leaves as vapour. Each kilogram of hydrogen makes nine kilograms of water, and vaporising that costs 2.442 MJ/kg at 25 C. Petrol at 46 MJ/kg with 14% hydrogen therefore delivers about 42.9 MJ/kg in an engine that exhausts steam.

Formulas

Water formed

water = 9 x hydrogen mass fraction

Lower heating value

LHV = HHV - 2.442 x water formed

Worked example

With the default values below, Fuel Heating Value Calculator returns Lower Heating Value of 42.923. Change any input above and every figure here is recalculated in your browser.

Inputs used

Higher heating valueminimum 0 MJ/kg: 46 MJ/kg
Hydrogen content by massaccepts 0–100 %: 14 %
Fuel densityminimum 0 kg/L: 0.75 kg/L

Results

Lower Heating Value: 42.923 MJ/kg
Water Formed Per Kilogram Of Fuel: 1.260 kg
Usable Energy Per Litre: 32.192 MJ/L
Lower Value As Share Of Higher: 93.31%

Step by step

1Values used
2Water formed
3Lower heating value
4Lower Heating Value= 42.923 MJ/kg
5Water Formed Per Kilogram Of Fuel= 1.260 kg
6Usable Energy Per Litre= 32.192 MJ/L
7Lower Value As Share Of Higher= 93.31

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Which value do engine efficiency figures use?

Almost always the lower value, because exhaust leaves hot and the water never condenses. Condensing boilers are the exception and are rated on the higher value.

Why the factor of nine?

Water is H2O: 2 g of hydrogen makes 18 g of water, so mass increases ninefold.