Calorific Value

What It Measures

Calorific value is the heat released by complete combustion of a unit mass of fuel, usually expressed in kcal/kg or MJ/kg. Gross calorific value (higher heating value, GCV/HHV) includes the latent heat of the water vapour formed during combustion; net calorific value (lower heating value, NCV/LHV) excludes it.

For charcoal the calorific value is a direct measure of energy content, unlike fixed carbon, which is a calculated proxy for the carbon-rich fraction.

Why It Matters

Calorific value is the most direct single measure of how much usable energy a fuel delivers per kilogram. For industrial heating and energy buyers it is a first-order specification.

It is also a check on fixed carbon: two charcoals can report similar fixed carbon but differ in calorific value because of ash composition and other factors.

Typical Measurement Method

Calorific value is measured by bomb calorimetry: a weighed sample is combusted in oxygen inside a sealed bomb, and the heat released is measured by the temperature rise of a surrounding water jacket, corrected for the heat of formation of acids and other factors.

Public references include ASTM D5865 for coal and coke and ISO 18125 for solid biofuels. The reported value (GCV or NCV) and the basis must be stated, because GCV and NCV differ and because moisture affects the as-received figure.

Buyer Relevance

Buyers who pay for energy should specify the calorific value, its type (GCV versus NCV) and its basis, and ask for the method. A calorific value without these is not comparable across suppliers.

For charcoal traded for hookah or BBQ, calorific value is usually less decisive than ash, size and burn behaviour, but it remains a useful energy check alongside fixed carbon.

Limitations

Calorific value depends on moisture and ash content: wetter or higher-ash material reports a lower as-received value. GCV and NCV are different quantities and must not be confused.

A calorific value describes energy content, not how the fuel burns in a particular appliance — burn rate and emissions are separate determinations. This page describes methodology only and publishes no calorific-value figures.

Data Source

Public standard methodology (general); not supplier-specific test data.

Last updated: 2026-10-07

Public methods commonly referenced

• ASTM D5865 — Gross calorific value of coal and coke
• ISO 18125 — Solid biofuels: determination of calorific value
• Bomb-calorimeter method (oxygen-bomb combustion)

Standard references are given as general, publicly documented method families. Applicability, current edition and reporting basis must be confirmed with the testing laboratory for any specific report.