All kinetic and equilibrium isotope effects result from differences in atomic mass. As a result, a reaction that fractionates S will also fractionate S and S, and the fractionation factor for each isotope will be mathematically proportional to its mass. Because of the mathematical relationships of their masses, the observed relationships between δS, δS, and δS in most natural materials are approximately δS = 0.515 × δS and δS = 1.90 × δS. Rarely, natural processes can create deviations from this relationship, and these deviations are reported as ΔS and ΔS values, usually pronounced as "cap delta." These values are typically calculated as follows:
:ΔS = 1000 × [(1 + δS/1000) − (1 + δS 1000) − 1]
:ΔS = 1000 × [(1 + δS/1000) − (1 + δS/1000) − 1]
However, the method for calculating ΔS and ΔS values is not standardized, and can differ among publications.