FIB-4 calculator
Estimate your Fibrosis-4 (FIB-4) index — a non-invasive screen for advanced liver fibrosis — from four routine numbers: age, AST, ALT, and platelet count. This tool applies the age-65 cutoff adjustment automatically.
Your privacy: this calculator runs entirely in your browser — nothing you type is sent anywhere. It's the same on-device principle Quanome is built on.
Educational reference only — not medical advice. FIB-4 is a non-invasive screening estimate for advanced fibrosis (best validated in NAFLD/MASLD and viral hepatitis), not a diagnosis. An indeterminate or high score is read with a clinician, usually with elastography (FibroScan) or further tests.
## What FIB-4 numbers mean
| FIB-4 index | Risk band (under 65) | Age 65+ |
| --- | --- | --- |
| Low | < 1.3 — advanced fibrosis unlikely | < 2.0 |
| Indeterminate | 1.3 – 2.67 — needs further testing | 2.0 – 2.67 |
| High | > 2.67 — advanced fibrosis more likely | > 2.67 |
In people **65 and older** the lower cutoff moves from 1.3 to **2.0**, because FIB-4 over-estimates fibrosis with age — this calculator applies it automatically. A **low** score is reassuring; **indeterminate** or **high** warrants a clinician's follow-up (often elastography), not a conclusion on its own.
## The formula
- **FIB-4 = (age × AST) ÷ (platelet count × √ALT)** — age in years, AST/ALT in U/L, platelets in ×10⁹/L (= ×10³/µL).
- It's a **non-invasive** score: it turns four numbers you probably already have into an estimate of advanced-fibrosis risk, so it's often used to decide who needs a FibroScan rather than to replace one.
## The markers behind it
FIB-4 is only a screen — read it with the values it comes from:
- **AST & ALT** — see [elevated liver enzymes (ALT & AST) explained](/blog/elevated-liver-enzymes-alt-ast-meaning/), and the enzyme pattern via the [AST/ALT ratio calculator](/tools/ast-alt-ratio-calculator/).
- **Platelets** — a low platelet count is part of what drives a high FIB-4; see [what your platelet count means](/blog/what-your-platelet-count-means/).
- On the same panel? Correct calcium for albumin with the [corrected calcium calculator](/tools/corrected-calcium-calculator/).
## Track your liver markers over time — privately
A single FIB-4 is a snapshot; the value is in the **trend**. [Quanome](/) pulls your labs, Apple Health, and even your DNA into one private timeline on your device — parsed locally, never uploaded — with an AI coach that reads your liver panel over time.
Track your liver markers over time, privately
Quanome unifies your labs, Apple Health, and DNA into one private, on-device timeline — with an AI coach. Free on the App Store and Google Play.
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