Convert your oils between standards
Several organizations (ISO, SAE, AGMA) have created competing standards to define oil viscosity ranges, but most of them mean the same thing. Oils grades that are on the same horizontal line (with the correct Viscosity Index) on the chart are equivalent.
ISO VG measures oil at 40ºC and a given range to +/-10% of their stated value, so ISO VG 100 oil will have a viscosity between 90 and 100 cSt at 40ºC.
AGMA has redefined its grades to align with ISO standards, so they line up exactly.
SAE measures oil at 100ºC. Oil gets thinner according to its Viscosity Index, and the chart is calculated with a specific Viscosity Index (VI 95 default)
The chart assumes the oil has a Viscosity Index of 95. This is a good approximation for most oils, but will lead to a small error when converting between ISO/AGMA and SAE for high Viscosity Index oils.
Viscosity Index: 95