Viscosity Index Calculator

If you know the viscosity of an oil at 40ºC and 100ºC, you can easily calculate its Viscosity Index (VI). The Viscosity Index is a measure of how much the viscosity changes with temperature; a higher VI indicates less change.

This calculator uses centi-Stokes (cSt), which are equivalent to mm^2/s. To get centiStokes from centiPoise, divide the centiPoise value by the fluid's density.

This calculator follows ASTM D2270 - 10 (Reapproved 2016), Standard Practice for Calculating Viscosity Index from Kinematic Viscosity at 40ºC and 100ºC

Viscosity Index is rounded to the nearest whole number. If halfway between (i.e. 13.5) it is rounded to the nearest even number. For example: (13.5 --> 14, 14.5 --> 14, 15.5 --> 16)