FIB-4 Index Calculator

Calculate the FIB-4 index to estimate liver fibrosis risk.

Aug 31, 2026 Clinical Chemistry #liver #fibrosis #noninvasive #fib4

Calculate

All fields required unless noted

Age (years)

AST (U/L)

ALT (U/L)

Platelet count (10⁹/L)

Calculating...

Enter your values and press Calculate to see the result.

Formula & Clinical Notes

Formula

FIB-4 = (Age × AST) ÷ (Platelet × √ALT)

Clinical Notes

FIB-4 = (age × AST) / (platelet count × √ALT), with age in years, enzymes in U/L and platelets in 10⁹/L. FIB-4 < 1.45 makes advanced fibrosis unlikely; FIB-4 > 3.25 makes advanced fibrosis likely; 1.45–3.25 is indeterminate and warrants further testing. Validated mainly in chronic hepatitis C, hepatitis B and NAFLD.

Sources

Sterling et al. (2006) — Development of a simple noninvasive index to predict significant fibrosis