C308 – ISO 6976:2016 Calorific Value and Relative Density


This calculates calorific values, density, relative density and Wobbe index from a gas composition. Results are calculated for the composition treated as both a real and an ideal gas, inferior (net) and superior (gross) calorific value and Wobbe index are displayed in each case. This version of the calculation included both the definitive and alternative methods of calculating the calorific value on a volumetric basis.


FLOCALC Calculation reference F110

Kelton calculation reference C308

Kelton calculation reference C111

ISO 6976:2016 Natural Gas – Calculation of calorific values, density, relative density and Wobbe indices from composition

ISO 13443:1996 Natural gas – Standard reference conditions


Hydrocarbon Tail

  • No Tail
  • C6 Tail
  • C7 Tail
  • C9 Tail

Select the appropriate hydrocarbon tail. Where a tail is selected the percentage split of each component is entered, this is generally obtained from laboratory analysis.

Reference Temperature (Combustion/Metering)

  • 25/0
  • 15/0
  • 0/0
  • 15/15
  • 25/20
  • 20/20
  • 25/15
  • 60/60
  • User entered reference conditions (ISO 13443)

This option is used to select the reference temperature used for the calculation. There is a choice of various combustion/metering temperatures used around the world or to manually enter base pressure, combustion and metering temperatures which will use the equations set out in ISO 13443:1996 to correct values from ISO standard conditions to those entered by the user.

Gas Analysis

  • Extended Analysis
  • Refinery/Trace Gases

These boxes can be checked to include a wider range of compounds in the composition.


This performs the calculations as per ISO 6976:2016 standard.