# APRI Calculator (AST to Platelet Ratio Index)

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

> The APRI calculator works out the AST to platelet ratio index, a simple blood-test score for liver fibrosis and cirrhosis recommended by the WHO for chronic hepatitis B and C.

## Inputs

- AST (U/L)
- AST upper limit of normal (U/L)
- Platelets (×10⁹/L)

## Results

- APRI
- Interpretation

## Formula

```
APRI = (AST ÷ AST upper limit of normal) ÷ platelets (×10⁹/L) × 100
< 0.5 significant fibrosis unlikely · > 1.5 significant fibrosis likely · > 2.0 cirrhosis likely (WHO)
```

## Explanation

APRI needs only two routine blood tests, which makes it useful where elastography is not available. It is best at ruling fibrosis in or out at the extremes.

### How to use the APRI Calculator

- **AST**
- **AST upper limit of normal**
- **Platelets**

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

### How it works

Enter AST, the lab's upper limit of normal and platelets.

### Inputs explained

FieldWhat to enterASTIn U/LAST upper limit of normalIn U/LPlateletsIn ×10⁹/L

### Example values

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

AST (U/L)APRI400.67601801.331001.6712021602.67
*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 — AST: 80 U/L; AST upper limit of normal: 40 U/L; Platelets: 150 ×10⁹/L.

Results — **APRI = 1.33**; Interpretation = Indeterminate.

## Key terms

- **APRI**: AST-to-platelet ratio index.

## FAQ

**What APRI suggests cirrhosis?**
Above 2.0 (WHO hepatitis guidelines).

**How accurate is APRI?**
Moderately – best for ruling out cirrhosis at low values.

**Can APRI be used in fatty liver disease?**
FIB-4 or NAFLD fibrosis score are preferred there.


## Sources

- [Wai CT et al. A simple noninvasive index can predict both significant fibrosis and cirrhosis in chronic hepatitis C. Hepatology, 2003](https://pubmed.ncbi.nlm.nih.gov/12883497/)