Rationale The isotope delta is calculated from the isotope ratio of a sample and the absolute isotope ratio of the zero reference point defining each stable isotope international scale ( R std ). Therefore, R std requires accurate determination. However, the literature contains a large number of R std values, and selection of different R std may lead to inconsistency in reporting and recalculating stable isotope results. Methods We reviewed R std used in the proprietary software provided by the manufacturers of stable isotope instruments commonly employed for analyses of stable HCNOS compositions. We compared the R std values and assessed the potential implications of using different R std and the normalization versus tank working gas standard for consistency in reporting stable isotope results. Results Different R std values are used by different manufacturers of stable isotope analytical instruments. For R ( 2 H/ 1 H) VSMOW two different but very similar values are used, 0.00015575 and 0.00015576; for R ( 13 C/ 12 C) VPDB three different values are used, 0.0111802, 0.0112372 and 0.01118028; and for R ( 15 N/ 14 N) Air‐N2 two values, 0.0036782 and 0.0036765, are used. All manufacturers are using the same value for R ( 18 O/ 16 O) VSMOW , 0.00200520, but three different values for R ( 18 O/ 16 O) VPDB , 0.002067200, 0.00208835 and 0.002088349. For R ( 34 S/ 32 S) VCDT four different R std are used, 0.0441509, 0.0441626, 0.044162589 and 0.0441520597. Conclusions The use of different R std values may lead to differences in the isotope delta values obtained if the normalization versus working standard gas is applied. For the range of R std used in proprietary software, the potential differences are lowest for oxygen (< 0.002 ‰) and nitrogen (< 0.001 ‰), and highest for carbon (0.107 to 0.112 ‰) and sulfur (0.023 ‰). Evaluation of the existing R std values and recommendations for the best estimates are highly desirable to ensure worldwide consistency in stable isotope data reporting.