FIB-4 Index Calculator (Liver Fibrosis)
The FIB-4 index estimates the likelihood of advanced liver fibrosis from age, AST, ALT and platelet count, helping decide who needs further fibrosis assessment. It is widely used to rule out advanced fibrosis in fatty liver disease and viral hepatitis.
Quick answer
FIB-4 = (age Γ AST) Γ· (platelets Γ βALT). It is a non-invasive index that helps rule out advanced liver fibrosis. Using the original Sterling 2006 cut-offs, a result under 1.45 makes advanced fibrosis unlikely, over 3.25 makes it likely, and in between is indeterminate.
FIB-4 inputs
How to use the FIB-4 calculator
- 1Enter age. Enter the patient age in years.
- 2Enter AST, ALT and platelets. Enter the AST and ALT (in U/L) and the platelet count (in 10βΉ/L, i.e. the standard lab value such as 200).
- 3Read the FIB-4 and band. The tool computes FIB-4 and shows the band: under 1.45 (low probability of advanced fibrosis), 1.45β3.25 (indeterminate), or over 3.25 (high probability) β to discuss with a clinician.
Medical disclaimer: This is general health information, not medical advice. It does not diagnose or treat any condition, and the results are estimates based on public reference formulas. Always consult a qualified doctor about your individual health. If you think you may have a medical emergency, contact your local emergency services immediately.
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Book a consultationFrequently asked questions
What is a normal FIB-4 score?β
There is no single "normal", but using the original Sterling 2006 cut-offs a FIB-4 under 1.45 has a high negative predictive value for advanced fibrosis. Many primary-care fatty-liver pathways use a lower threshold of 1.30 to rule out advanced fibrosis, especially under age 65.
What FIB-4 score is concerning?β
A FIB-4 above 3.25 (or 2.67 in some guidelines) suggests a higher probability of advanced fibrosis and usually prompts referral for further assessment, such as elastography or specialist review. A clinician interprets it.
Does FIB-4 replace a liver biopsy?β
No. FIB-4 is a screening index to decide who needs further testing. It cannot confirm or stage fibrosis on its own; imaging (for example FibroScan) or biopsy may still be needed. It is also less reliable at the extremes of age.
Is my data stored?β
No. The calculator runs entirely in your browser; nothing you enter is sent to a server.
Sources & validation
This calculator reproduces the published FIB-4 score, validated for non-invasive estimation of advanced liver fibrosis (stage 3β4) in adults.
- Sterling RK, Lissen E, Clumeck N, et al. Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection (Hepatology 2006;43:1317-1325) β the FIB-4 derivation paper (cut-offs 1.45 and 3.25) β verified 2026-06-18
- AASLD/AGA NAFLDβNASH guidance: FIB-4 < 1.30 rules out advanced fibrosis, > 2.67 suggests it, in primary-care risk pathways β verified 2026-06-18
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