Engineering tools · Viscosity index

Viscosity Index Calculator

Viscosity index (VI) measures how much a lubricant's viscosity changes with temperature. A higher VI means more stable performance across a wider operating temperature range.

Enter kinematic viscosity at 40 °C and 100 °C to calculate VI using the standard method.

ASTM D2270 · APPENDIX X2
01 Kinematic viscosity
cSt
cSt
—
VISCOSITY INDEX
–
03580110200
Enter both viscosities to see the result.
KV @ 40 °C
–
cSt
KV @ 100 °C
–
cSt
02 Viscosity–temperature curve
Enter both viscosities to plot the curve.

Calculated using the piecewise quadratic method from ASTM D2270 Appendix X2, matched to the standard's own reference tables to within approximately 0.1%.

This tool is intended for guidance. For certified or regulatory results, verify against a laboratory determination.