12326 IUPAC Gold Book - accurate mass 10.1351/goldbook.12326 12326 current 1 Experimentally determined mass of an ion of known charge. Can be used to determine elemental composition to within limits defined by both the accuracy and precision of the measurement. Accurate mass and exact mass are not synonymous. Accurate mass refers to a measured mass, and exact mass refers to a calculated mass. exact mass https://goldbook.iupac.org//terms/view/12407 PAC, 2013, 85, 1515. 'Definitions of terms relating to mass spectrometry (IUPAC Recommendations 2013)' on page 1519 (https://doi.org/10.1351/PAC-REC-06-04-06) https://goldbook.iupac.org/terms/view/12326/html https://goldbook.iupac.org/terms/view/12326/json https://goldbook.iupac.org/terms/view/12326/plain Citation: 'accurate mass' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.12326 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using. 2026-07-12T15:27:23+00:00