Cetane Index (ASTM D976)

Estimate cetane index from density and mid-boiling point (T50) - the lab proxy for actual cetane number on distillate fuels.

FuelDistillate

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This calculator requires JavaScript to compute its result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

CI = 454.74 - 1641.416 \cdot SG + 774.74 \cdot SG^2 - 0.554 \cdot T_{50} + 97.803 \cdot (\log T_{50})^2

Symbol	Meaning	Unit
$SG$	Specific gravity at 60 °F
$T_{50}$	Mid-boiling point at 50 % recovery	°F
$CI$	Cetane Index

Source: ASTM D976

Estimate cetane index from density and mid-boiling point (T50) - the lab proxy for actual cetane number on distillate fuels.