The article considers the current methods of measuring the calorific value of natural gas which are valid in the upto-date gasometry. The procedure for measuring the gross and net volume-basis specific calorific value of natural gas by the calorimetric method is analyzed. It is shown that to increase the accuracy and validity of measurement results, the experiment to determine the values of gross and net volume-basis specific calorific should be performed for at least 5 samples of the investigated gas. A methodology for estimating the accuracy of measuring the gross and net volume-basis specific calorific values of natural gas by the calorimetric method by finding estimates of the uncertainty of the obtained measurement results taking into account both random and systematic influencing factors are developed. The uncertainty budgets for measuring the gross and net volumebasis-specific calorific values of natural gas have been developed for the practical implementation of the methodology. The results of experimental studies of samples of one of the natural gas fields are given and the objective values of the gross and net volumebasis specific calorific with estimates of extended uncertainty are obtained.
 V. Motalo, B. Stadnyk, A. Motalo, “Evaluation of Natural Gas Quality by its Calorific Value”, Measuring Equipment and Metrology, vol.82, no.1, p.30-36, 2021, [Online], Available: https://doi.org/10.23939/istcmtm2021.01.030
 V. Motalo, B. Stadnyk, A. Motalo, I. Likhnovsky, “Hydrocarbon Gases Quality: Impact on Sustainable Development Goals and Environment”, in Sustainable Production: Novel Trends in Energy, Environment and Material Systems, G.M. Krolczyk, and others, Eds. Part 8, Springer, p.105-129, 2020.[Online], Available: https://doi.org/10.1007/978-3-030-11274-5_
 ISO 13686:2013 Natural gas: Quality designation. – Reviewed and confirmed in 2020. – ISO, 2013.
 ISO 13443:1996 Natural gas: Standard reference conditions. – Reviewed and confirmed in 2020. – ISO, 1996.
 ISO 14532:2014 Natural gas: Vocabulary. – Reviewed and confirmed in 2020. – ISO, 2014.
 P. Ulbig, D. Hoburg, “Determination of the calorific value of natural gas by different methods”, Thermochimica Acta 382(1):27-35, vol.382, no.1–2, p. 27-35, 2002, [Online], Available: https://doi.org/10.1016/S0040-6031(01)00732-8
 C. Villermaux, M. Zarea1, F. Haloua, B. Hay, J.-R. Filtz, “Measurement of Gas Calorific Value: A New Frontier to be Reached with an Optimized Reference Gas Calorimeter”, in Proc. 23rd World Gas Conference, Amsterdam, 2006. [Online], Available: http://members.igu.org/html/wgc2006/pdf/paper/add 12646.pdf
 J. Markowski, P. Imilkowski, M. Nowacki, D. Olejniczak, J. Madry, K. Netter, R. Jesionek, G. Wieczorkiewicz , “The concept of measurement of calorific value of gaseous fuels”, in Proc. E3S Web of Conferences 207, 010 PEPM'2020, 25, 2020. [Online], Available: https://doi.org/10.1051/e3sconf/202020701025
 A. Zajc, T. Ryll, “Rapid determination of the calorific value by means of a novel gas quality sensor”, Measuring & Process Control Reports, 2017-01-Heat Processing, 2017. [Online], Available: https://www.meterq.de/assets/ images/downloads/2017-01-Heat%20Processing.pdf
 R. Hamaguchi, “Natural Gas Measurement Using Temperature-Dependent Thermal Conductivity”, Technical Review 2018 – Azbil Corporation, 2018. [Online], Available: https://www.azbil.com/corporate/technology/review/pdf/rev2018E _4.pdf
 ISO 15112:2018 Natural gas: Energy determination, 2018
 ISO 6974-1:2012 Natural gas: Determination of composition and associated uncertainty by gas chromatography, Part 1: General guidelines and calculation of composition. – Reviewed and confirmed in 2018. 2012.
 ISO 6976:2016 Natural gas: Calculation of calorific values, density, relative density and Wobbe index from composition. – ISO, 2016.
 ISO 15971:2008 Natural gas: Measurement of properties. Calorific value and Wobbe index. – Reviewed and confirmed in 2020: – ISO, 2013. [Online], Available: https://www.iso.org/standard/44867.html
 ASTM D1826-94 Standard Test Method for Calorific (Heating) Value of Gases in Natural Gas Range by Continuous Recording Calorimeter, ASTM International, West Conshohocken, PA, 2017. [Online], Available: https://doi.org/10.1520/D1826-94R17
 GOST 27193-86. Natural combustible gases: Method for determination of calorific value with water calorimeter. – Reviewed and confirmed in 2021 (in Russian). [Online], Available: https://files.stroyinf.ru/Index2/1/4294827/ 4294827433.htm
 ISO/IEC 17025:2017, General Requirements for the Competence of Testing and Calibration Laboratories, 2017. – ISO, 2017.
 ISO/IEC Guide 98-3:2008, Uncertainty of measurement, Part 3: Guide to the expression of uncertainty in measurement, 2008.
 EA-4/02 M: 2013, Expression of the Uncertainty of Measurement in Calibration: European Accreditation, 2013.