FIB-4 Liver Fibrosis Calculator

About this calculator

The FIB-4 index is a non-invasive liver fibrosis screening score calculated from age, AST, ALT and platelet count using the formula FIB-4 = (Age × AST) / (Platelets × √ALT), originally validated in patients with hepatitis C and now widely used across chronic liver disease, including non-alcoholic fatty liver disease (NAFLD/NASH). A low score helps rule out advanced fibrosis with reasonable confidence, a high score flags patients who likely need further workup, and an intermediate score is indeterminate.

Primary care physicians, hepatologists and gastroenterologists use FIB-4 as a first-line triage tool to decide which patients with fatty liver disease or other chronic liver conditions need referral for elastography or biopsy, since it can be calculated from routine bloodwork already on file rather than requiring a new invasive procedure just to screen.

This calculator takes your age, AST, ALT and platelet count and returns your FIB-4 score along with its fibrosis risk category.