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FIB-4 Calculator

Estimate FIB-4 liver fibrosis risk from age, AST, ALT, and platelet count. Results are screening estimates, not a diagnosis.

FIB-4 index inputs

Whole years. Age sits in the numerator, so older age raises FIB-4.

Aspartate aminotransferase from a liver panel, in U/L (same as IU/L).

Alanine aminotransferase, in U/L. Must be above 0 (it sits under a square root in the formula).

Enter the count in 10^9/L (the same number as 1000/uL). A reading of 200,000 per uL is entered as 200.

FIB-4 index

2.26

Indeterminate

The result is inconclusive. Most guidelines recommend a second-line test such as transient elastography (FibroScan) or an ELF blood test.

Interpretation cutoffs applied

Low-risk threshold (rule out)
< 1.30
High-risk threshold (rule in)
> 2.67

Standard cutoffs for adults under 65. For patients 65 or older, the low-risk threshold rises to 2.00.

Medical disclaimer

This calculator is for educational use only and is not a diagnosis or a substitute for professional medical advice. FIB-4 is a screening index, not a confirmatory test: it can be skewed by acute hepatitis, recent transfusion, or platelet disorders, and its cutoffs vary by population. Discuss your liver enzymes, platelet count, and FIB-4 score with your clinician before drawing any conclusions.

Frequently Asked Questions about the FIB-4 Calculator

What is the FIB-4 index?
FIB-4 (Fibrosis-4) is a noninvasive score that estimates the likelihood of advanced liver fibrosis using four routine values: your age, AST, ALT, and platelet count. It was developed by Sterling and colleagues in 2006 and is now widely used to screen people with fatty liver disease (NAFLD/MASLD) or chronic hepatitis, often to decide who needs a follow-up test like FibroScan.
How is FIB-4 calculated?
The formula is FIB-4 = (age in years times AST) divided by (platelet count times the square root of ALT). AST and ALT are entered in U/L (the same as IU/L), and the platelet count is entered in 10^9/L, which is the same number as 1000 per microliter. For example, a platelet reading of 200,000 per microliter is entered as 200.
What do the FIB-4 result bands mean?
A score below 1.30 is low risk and effectively rules out advanced fibrosis. A score above 2.67 is high risk and suggests advanced fibrosis is likely. Anything in between is indeterminate, where guidelines usually recommend a second-line test such as transient elastography (FibroScan) or an ELF blood test rather than a firm conclusion.
Why does the cutoff change for people over 65?
Age sits in the numerator of the FIB-4 formula, so the score rises mechanically as you get older, which makes the standard 1.30 threshold flag too many healthy older adults. To keep the score useful, McPherson and colleagues (2017) recommend raising the low-risk cutoff to 2.00 for people older than 65. This calculator applies that higher threshold automatically when the entered age is above 65.
What can throw off a FIB-4 score?
FIB-4 is a screening estimate, not a confirmatory test. Acute hepatitis or a sudden flare can spike AST and ALT, and a low platelet count from a transfusion, bone marrow condition, or unrelated illness can inflate the result independent of liver scarring. Validated cutoffs also vary by underlying disease and population, so the same number can mean slightly different things in different settings.
Is this calculator a substitute for medical advice?
No. This tool is for education only and is not a diagnosis or a substitute for professional medical advice. FIB-4 helps decide whether further evaluation is warranted, but only a clinician can interpret it alongside your full history, imaging, and other labs. Discuss any result with your doctor before drawing conclusions or changing anything.

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