Key points
- For healthcare professionals assessing adults with known or suspected MASLD.
- It estimates the chance of advanced fibrosis (F3–F4). It does not diagnose MASLD or MASH.
- It is a first step. Results of 1.3 or more need a second test.
- Runs only in the browser. Nothing typed is stored or sent.
For the evidence, graded recommendations, a case and self-test questions, read Module 1: Assessing liver fibrosis in MASLD.
1Formula and units
FIB-4 = (age in years × AST in U/L) ÷ (platelets in 10⁹/L × √ALT in U/L).
Platelets in 10⁹/L are the same number as in 10³/µL. Use AST and ALT taken on the same day.
| Input | Accepted range |
|---|---|
| Age | 18–100 years |
| AST | Above 0 and below 5000 U/L |
| ALT | Above 0 and below 5000 U/L |
| Platelets | Above 0 and below 2000 ×10⁹/L |
Worked example: age 55, AST 40, ALT 35, platelets 200 → (55 × 40) ÷ (200 × 5.92) = 1.86 → indeterminate.
2How results are labelled
| Score | Label |
|---|---|
| Below 1.3 (below 2.0 if aged 65+) | Low risk |
| From the low cut-off up to below 2.67 | Indeterminate |
| 2.67 or above | High risk |
Cut-offs from the EASL–EASD–EASO 2024 and AASLD 2023 guidance; the age-65 cut-off from McPherson 2017.
3Do not rely on FIB-4 alone when
- The patient is under 35 (accuracy is poor). The calculator shows a warning.
- AST or ALT is very high, or there is acute liver injury. The calculator warns above 200 U/L.
- Platelets are low for another reason (e.g. blood disease, hypersplenism from another cause, recent chemotherapy).
- There are clinical or imaging signs of cirrhosis. A low score does not exclude it.
- Another liver disease is present. FIB-4 cut-offs here are for MASLD.
- Children and pregnancy: not validated.
4How we check the calculator
The code is public on GitHub. Before each change we test known values, including the worked example above and the cut-off edges (1.29, 1.30, 2.66, 2.67), and both age groups. Report a problem by email.
Related topics
References
- Sterling RK, et al. Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection. Hepatology 2006;43:1317–25. doi:10.1002/hep.21178
- Shah AG, et al. Comparison of noninvasive markers of fibrosis in patients with nonalcoholic fatty liver disease. Clin Gastroenterol Hepatol 2009;7:1104–12. doi:10.1016/j.cgh.2009.05.033
- McPherson S, et al. Age as a confounding factor for the accurate non-invasive diagnosis of advanced NAFLD fibrosis. Am J Gastroenterol 2017;112:740–51. doi:10.1038/ajg.2016.453
- EASL–EASD–EASO Clinical Practice Guidelines on the management of MASLD. J Hepatol 2024;81:492–542. doi:10.1016/j.jhep.2024.04.031
- Rinella ME, et al. AASLD Practice Guidance on the clinical assessment and management of NAFLD. Hepatology 2023;77:1797–835. doi:10.1097/HEP.0000000000000323
How to cite this page
Desoky M. FIB-4 calculator: method, users and limits. Metabolic Liver Academy quick reference, version 1.0. Updated 2026-10-03. Available from: https://drmahmouddesoky.github.io/metabolic-liver-academy/ref/fib4-method.html
A summary of published guidelines for healthcare professionals. It does not replace clinical judgement, the full guidelines or local drug labels. Disclaimer.