Calculate the FIB-4 index from age, AST, ALT and platelet count. FIB-4 is a first-line non-invasive tool used to estimate the risk of advanced liver fibrosis, including in people with metabolic dysfunction-associated steatotic liver disease (MASLD).
FIB-4 Liver Fibrosis Calculator
If your platelet count is shown as 200 ×10³/µL, enter 200.
Values are calculated in your browser and are not sent to or stored on the server.
What is FIB-4?
The Fibrosis-4 (FIB-4) index combines age, AST, ALT and platelet count. It is a non-invasive risk-stratification tool, not a diagnostic test. It is widely used to identify people with a low likelihood of advanced fibrosis and those who may need a second assessment.
Formula
FIB-4 = age (years) × AST (U/L) / [platelets (10⁹/L) × √ALT (U/L)]
Example: age 55, AST 40 U/L, ALT 50 U/L and platelets 200×10⁹/L gives a FIB-4 of about 1.56.
How to read the result
| Age | FIB-4 | Common interpretation |
|---|---|---|
| 35–64 | <1.3 | Lower-risk range |
| 35–64 | 1.3–2.67 | Indeterminate; consider second-line assessment |
| 35–64 | >2.67 | Higher-risk range |
| 65+ | <2.0 | Age-adjusted lower-risk range |
| 65+ | 2.0–2.67 | Further assessment range |
| 65+ | >2.67 | Higher-risk range |
FIB-4 performs less reliably below age 35. A low value should not be used alone to rule out advanced fibrosis when clinical risk is high.
When can FIB-4 be misleading?
- Acute hepatitis or temporary large AST/ALT elevations
- Low platelets for reasons unrelated to portal hypertension or liver disease
- Alcohol, medications or muscle injury affecting AST
- Older age, which can raise the score independently
What happens after FIB-4?
A low score does not exclude every liver condition, and a high score does not diagnose cirrhosis. In people with a score above the first-line threshold or substantial clinical risk, clinicians may use vibration-controlled transient elastography (VCTE/FibroScan), ELF or other tests.
How to use this calculator
- Find your age, AST, ALT and platelet count on the same or clinically comparable set of laboratory results.
- Check the units before entering the values.
- Review both the numeric score and the age-specific interpretation.
- If the result is indeterminate/high or liver tests remain abnormal, discuss the original laboratory report with a clinician.
Related tools and resources
Health calculator hub · BMI calculator · Waist-to-height ratio calculator · HbA1c↔eAG calculator · Health checkup result guide · Health records and visit preparation · 한국어
Sources
- AASLD: non-invasive assessment in MASLD
- EASL–EASD–EASO MASLD Clinical Practice Guidelines
- Sterling et al. 2006, original FIB-4 development study