This International Standard sets out criteria for the calibration of extensometer systems, covering general principles, the calibration equipment to be used, pre-calibration inspection and the measurement of gaugelength for various types of extensometer systems. Aspects of the calibration process are addressed, as are the assessment of the results, uncertainties, calibration intervals and reporting. Criteria for calibration apparatus, their calibration and grading are also addressed, complemented by a Bibliography covering a number of important papers related to extensometer systems and their application. Work is in progress to develop processes for dynamic extensometer calibration; however at the time of writing of this standard these have not reached the level of development appropriate for inclusion within this International Standard. Informative annexes address calculation of uncertainties of measurement for an extensometer system calibration (Annex A), calibration of calibration apparatus (Annex B) and an example of a calibration report (Annex C). Subsequent annexes address examples of extensometer system configurations (Annex D), laser extensometry (Annex E), video extensometry (Annex F), full field extensometry (Annex G) and calibration of a crosshead measurement system (Annex H). This International Standard specifies a method for the static calibration of extensometer systems used in uniaxial testing, including axial and diametral extensometer systems, both contacting and non-contacting. This document (EN ISO 9513:2012) has been prepared by Technical Committee ISO/TC 164 "Mechanical testing of metals", Subcommittee 1 "Unaxial testing" (secretariat: AFNOR, France) and has been adopted under the Vienna Agreement by ECISS/TC 101 "Test methods for steel (other than chemical analysis)" (secretariat: AFNOR, France). The responsible German committee is Working Committee is NA 062-08-11 AA "Werkstoffprüfmaschinen" of the Materials Testing Standards Committee (NMP).