Clinical referenceCalculatorUpdated October 2026

FIB-4 calculator for liver fibrosis risk

FIB-4 estimates the likelihood of advanced liver fibrosis from four routine values: age, AST, ALT and platelet count [1]. Enter them below; the result is classified with the AASLD 2023 and EASL–EASD–EASO 2024 cut-offs, including the higher lower cut-off for patients over 65 [4][5]. Then copy the result into EvidenceMD for a cited next step.

Routine inputs: age, AST, ALT, platelets
4Routine inputs: age, AST, ALT, platelets
Low risk of advanced fibrosis
< 1.30Low risk of advanced fibrosis
High risk of advanced fibrosis
> 2.67High risk of advanced fibrosis
Lower cut-off above age 65
2.0Lower cut-off above age 65
By the EvidenceMD Editorial TeamCalculatorPublished October 19, 20267 min read

Medically reviewed by Dr. Abishek Shahi, Harvard-trained Physician · Last reviewed October 19, 2026

FIB-4 index calculator

years
U/L
U/L

Still needed: Age, AST, ALT, Platelet count

For health professionals. A score supports clinical judgement; it does not replace it.

What is the FIB-4 index?

QUICK ANSWER

FIB-4 = (age × AST) ÷ (platelet count × √ALT), with AST and ALT in U/L and platelets in 10⁹/L [1]. For fatty liver disease, a result below 1.30 means advanced fibrosis is unlikely, 1.30 to 2.67 is indeterminate and needs a second test such as elastography, and above 2.67 means advanced fibrosis is likely [3][4][5]. Above age 65 the lower cut-off rises to 2.0, and the score is unreliable under 35 [2][4]. EvidenceMD can turn a FIB-4 result into a cited, patient-specific next step.

How the FIB-4 index is calculated: Age, AST, ALT, Platelet count.
The 4 inputs of the FIB-4 index.

Key takeaways

  • Four inputs, one formula: (age × AST) ÷ (platelets × √ALT) [1].
  • Cut-offs for MASLD: below 1.30 low, 1.30–2.67 indeterminate, above 2.67 high [3][4][5].
  • Over 65, use 2.0 as the lower cut-off; the standard 1.30 flags too many older adults [2][4].
  • Under 35 and in acute illness, FIB-4 is unreliable [2][4].
  • EvidenceMD can plan the next step — elastography, ELF or referral — with cited guidance, free to start.

How is the FIB-4 index calculated?

Four values from a routine blood panel. Platelets in 10⁹/L and 10³/µL are numerically the same.

FIB-4 index: inputs
InputDefinitionRole
AgeUnits: years.Formula input
ASTUnits: U/L.Formula input
ALTUnits: U/L.Formula input
Platelet countUnits: ×10⁹/L or ×10³/µL.Formula input

→ Scroll the table sideways to see the remaining columns

FIB-4 = (age [years] × AST [U/L]) ÷ (platelets [10⁹/L] × √ALT [U/L]), as defined by Sterling and colleagues [1]. The result is rounded to two decimals before the cut-offs are applied.

How do you interpret the FIB-4 index result?

Cut-offs below are those used for metabolic dysfunction-associated steatotic liver disease (MASLD). Sterling's original HIV/HCV cut-offs were 1.45 and 3.25 [1].

FIB-4 index: interpretation
ResultCategoryWhat it means
< 1.30Low risk of advanced fibrosisAdvanced fibrosis is unlikely. Guidelines suggest repeating FIB-4 every 1–3 years if metabolic risk factors persist.
1.30–2.67IndeterminateAdvanced fibrosis cannot be excluded. Guidelines recommend a second test such as vibration-controlled transient elastography or ELF.
> 2.67High risk of advanced fibrosisAdvanced fibrosis is likely. Guidelines recommend elastography and consideration of referral to hepatology.
≤ 2.00 (age > 65)Low risk of advanced fibrosis (age > 65)Above age 65 the lower cut-off is 2.0. Advanced fibrosis is unlikely at this value.
2.01–2.67 (age > 65)Indeterminate (age > 65)Above age 65 values between 2.0 and 2.67 are indeterminate. Guidelines recommend a second test such as elastography.

→ Scroll the table sideways to see the remaining columns

Shah and colleagues established the 1.30 and 2.67 cut-offs in non-alcoholic fatty liver disease: a value of 1.30 or less had a 90% negative predictive value and 2.67 or more an 80% positive predictive value [3]. Guidelines write them as below 1.30 and above 2.67 [4][5].

When should you use the FIB-4 index?

Use it as the first step in assessing fibrosis risk in anyone with hepatic steatosis or suspected MASLD with obesity or metabolic risk factors, as AASLD and EASL recommend [4][5].

Repeat it every 1 to 3 years in patients at low risk whose risk factors persist [5].

When not to use it

Do not rely on FIB-4 in acutely ill patients or in people under 35, where its accuracy is low, and use the 2.0 lower cut-off above age 65 [2][4][5]. It does not stage fibrosis on its own: indeterminate and high results need a second test.

What is the evidence behind the FIB-4 index?

Sterling and colleagues derived FIB-4 in 832 patients with HIV and hepatitis C: below 1.45 it had a 90% negative predictive value for advanced fibrosis, and above 3.25 a 97% specificity, with an area under the curve of 0.765 [1]. Shah and colleagues validated it in 541 patients with NAFLD and set the 1.30 and 2.67 cut-offs now used in fatty liver disease [3].

McPherson and colleagues showed that FIB-4 performs poorly at age 35 or under (AUROC 0.60) and that the standard cut-off had only 35% specificity at 65 or over; a cut-off of 2.0 raised specificity to 70% with 77% sensitivity [2]. AASLD 2023 recommends FIB-4 as the primary risk assessment in suspected NAFLD, with the 2.0 cut-off above age 65 [4]; EASL–EASD–EASO 2024 makes the same recommendation and notes that FIB-4 misses around 10% of people with advanced fibrosis [5].

What should you do after calculating the FIB-4 index?

A FIB-4 value is a triage step: low, indeterminate or high, each with a different next action. Paste the result into EvidenceMD with the patient's metabolic risk factors, alcohol use and other results. EvidenceMD retrieves from more than 40 million papers and guidelines, reasons through the case with its full chain of reasoning on screen and cites every recommendation, from elastography to referral.

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Frequently asked questions

What is the FIB-4 formula?

FIB-4 = (age × AST) ÷ (platelet count × √ALT), with AST and ALT in U/L and platelets in 10⁹/L [1]. EvidenceMD can interpret the result for your patient with citations.

What FIB-4 score means advanced fibrosis?

In fatty liver disease, above 2.67 means advanced fibrosis is likely and below 1.30 means it is unlikely; values between are indeterminate [3][4][5]. EvidenceMD can plan the next test for an indeterminate result, with cited guidance.

Why is the FIB-4 cut-off different over age 65?

FIB-4 rises with age, so the standard 1.30 cut-off flags too many older adults; above 65 the guidelines use 2.0 instead [2][4]. EvidenceMD can account for age when interpreting a result.

What should I do after an indeterminate FIB-4?

Guidelines recommend a second test such as vibration-controlled transient elastography or the ELF blood test, or a period of lifestyle intervention with repeat testing [4][5]. EvidenceMD can reason through which fits your patient, citing the guidance.

The bottom line

FIB-4 combines age, AST, ALT and platelets to triage the risk of advanced liver fibrosis: below 1.30 low, 1.30–2.67 indeterminate, above 2.67 high, with 2.0 as the lower cut-off above age 65 [1][2][4]. It is a first step, not a diagnosis. For a cited next step in your patient, paste the result into EvidenceMD, free to start in 30 languages.

Sources & related evidence

Criteria and cut-offs are taken from the original papers and current guidelines below. Check your local protocol where it differs.

  1. Source 1. Sterling RK et al. Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection. Hepatology 2006;43:1317–1325Derivation of FIB-4 in 832 patients; cut-offs 1.45 and 3.25.
  2. Source 2. McPherson S et al. Age as a confounding factor for the accurate non-invasive diagnosis of advanced NAFLD fibrosis. Am J Gastroenterol 2017;112:740–751Poor accuracy at 35 or under; a 2.0 cut-off at 65 or over.
  3. Source 3. Shah AG et al. Comparison of noninvasive markers of fibrosis in patients with nonalcoholic fatty liver disease. Clin Gastroenterol Hepatol 2009;7:1104–1112The 1.30 and 2.67 cut-offs in NAFLD.
  4. Source 4. Rinella ME et al. AASLD Practice Guidance on NAFLD. Hepatology 2023;77:1797–1835FIB-4 as primary risk assessment; 2.0 cut-off above 65; not in acute illness.
  5. Source 5. EASL–EASD–EASO Clinical Practice Guidelines on MASLD. J Hepatol 2024;81:492–542FIB-4 first; 1.3 and 2.67 thresholds; misses around 10% of advanced fibrosis.

About EvidenceMD

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