# FIB-4 Calculator (Liver Fibrosis)

URL: https://speedycalculator.com/calculators/health/fib-4/
Last updated: 2026-10-30

> The FIB-4 calculator estimates the likelihood of advanced liver fibrosis from age, AST, ALT and platelet count. It is the recommended first test for fibrosis in fatty liver disease and hepatitis.

## Inputs

- Age (years)
- AST (U/L)
- ALT (U/L)
- Platelets (×10⁹/L)

## Results

- FIB-4
- Risk of advanced fibrosis

## Formula

```
FIB-4 = age × AST ÷ (platelets (×10⁹/L) × √ALT)
< 1.3 low risk (< 2.0 if age ≥ 65) · 1.3–2.67 indeterminate · > 2.67 high risk of advanced fibrosis
```

## Explanation

FIB-4 uses routine blood tests to identify people who are unlikely to have advanced fibrosis and can be managed in primary care. Indeterminate results are usually followed by elastography (FibroScan) or an ELF test.

### How to use the FIB-4 Calculator

- **Age**
- **AST**
- **ALT**
- **Platelets**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter age, AST, ALT and platelet count from the same blood test.

### Inputs explained

FieldWhat to enterAgeIn yearsASTIn U/LALTIn U/LPlateletsIn ×10⁹/L

### Example values

How the main result changes when **Age** changes and everything else stays at the example values above:

Age (years)FIB-427.50.8241.251.23551.6468.752.0582.52.461103.28
*Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.*

## Worked example

Inputs — Age: 55 years; AST: 40 U/L; ALT: 45 U/L; Platelets: 200 ×10⁹/L.

Results — **FIB-4 = 1.64**; Risk of advanced fibrosis = Indeterminate – consider elastography.

## Key terms

- **Fibrosis**: Scarring of the liver.

## FAQ

**What is a normal FIB-4?**
Below 1.3 (below 2.0 if 65 or older).

**Is FIB-4 reliable under 35?**
It is less accurate in young people.

**What comes after an indeterminate FIB-4?**
Usually transient elastography (FibroScan) or the ELF blood test.


## Sources

- [Sterling RK et al. Development of a simple noninvasive index to predict significant fibrosis in HIV/HCV coinfection (FIB-4). Hepatology, 2006](https://pubmed.ncbi.nlm.nih.gov/16729309/)