# 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)