Fatty Liver Index (FLI) Calculator

Fatty Liver Index (FLI) Calculator for Gastroenterology. The FLI is interpreted in three bands anchored to the original likelihood ratios. FLI below 30 (negative likelihood ratio ~0.2) makes steatosis unlikely and effectively rules it out; FLI of 60 or higher (positive likelihood ratio ~4.3) rules steatosis in and warrants confirmatory ultrasound plus screening for advanced fibrosis. Scores of 30 to 59 are indeterminate and neither confirm nor exclude fatty liver, so clinical judgment or direct imaging is needed. A high FLI should trigger intensified lifestyle counselling (weight loss, dietary change, exercise) and comorbidity optimization, not reassurance about liver fibrosis, which the index does not measure.

How this calculator works

The FLI is a logistic-regression-derived algorithm that estimates the probability of ultrasound-detectable hepatic steatosis from four routinely available variables: BMI, waist circumference, serum triglycerides, and gamma-glutamyl transferase (GGT). These are combined into a linear predictor (y = 0.953·ln[triglycerides in mg/dL] + 0.139·BMI + 0.718·ln[GGT in U/L] + 0.053·waist in cm − 15.745), which is then transformed by the logistic function FLI = (e^y / (1 + e^y)) × 100 to yield a score from 0 to 100. It quantifies steatosis likelihood, not fibrosis, inflammation, or hepatocyte injury.

When to use this calculator

Use the FLI as a first-pass, no-imaging screen for hepatic steatosis in adults with cardiometabolic risk factors (type 2 diabetes, obesity, metabolic syndrome) or as an epidemiologic surrogate for fatty liver in cohort studies. It is well suited to triaging who should proceed to ultrasound or a fibrosis-staging pathway. It should not be used to diagnose or stage fibrosis (use FIB-4 and elastography instead per EASL-EASD-EASO), nor in patients with significant alcohol intake, decompensated liver disease, or conditions that independently elevate GGT (cholestasis, enzyme-inducing drugs), which inflate the score without reflecting steatosis.

Inputs used

  • BMI
  • Waist circumference
  • Triglycerides
  • Gamma-glutamyl transferase

Clinical interpretation

The FLI is interpreted in three bands anchored to the original likelihood ratios. FLI below 30 (negative likelihood ratio ~0.2) makes steatosis unlikely and effectively rules it out; FLI of 60 or higher (positive likelihood ratio ~4.3) rules steatosis in and warrants confirmatory ultrasound plus screening for advanced fibrosis. Scores of 30 to 59 are indeterminate and neither confirm nor exclude fatty liver, so clinical judgment or direct imaging is needed. A high FLI should trigger intensified lifestyle counselling (weight loss, dietary change, exercise) and comorbidity optimization, not reassurance about liver fibrosis, which the index does not measure.

Worked example

A 54-year-old man with BMI 31 kg/m², waist 108 cm, triglycerides 210 mg/dL, and GGT 65 U/L. Computing y = 0.953·ln(210) + 0.139·31 + 0.718·ln(65) + 0.053·108 − 15.745 ≈ 0.953·5.347 + 4.309 + 0.718·4.174 + 5.724 − 15.745 ≈ 5.096 + 4.309 + 2.997 + 5.724 − 15.745 = 2.381. Then FLI = (e^2.381 / (1 + e^2.381)) × 100 ≈ (10.82 / 11.82) × 100 ≈ 92. An FLI of 92 (≥60) rules in hepatic steatosis and flags this patient for confirmatory imaging and a fibrosis-risk assessment.

Limitations and safety notes

The FLI was derived and validated against ultrasound, an insensitive standard that misses steatosis below roughly 20-30% fat content, so mild steatosis can be scored as negative. Because BMI and waist heavily weight the score, it performs poorly at extremes of body habitus and its cutoffs are less accurate in lean MASLD and in some East Asian populations where fatty liver occurs at lower BMI. GGT elevation from alcohol, biliary disease, or medications falsely raises the index, and the score says nothing about fibrosis stage, the true driver of liver-related outcomes. The 30-59 indeterminate zone is common in real-world cardiometabolic clinics, limiting decisiveness.

Frequently asked questions

Does the FLI diagnose or stage liver fibrosis?

No. The FLI estimates only the probability of hepatic steatosis (fat accumulation). It carries no information about fibrosis, which is the main predictor of liver-related mortality. Advanced fibrosis must be assessed separately with FIB-4 and, if needed, transient elastography, as recommended by the EASL-EASD-EASO MASLD guideline.

What do the cutoffs of 30 and 60 mean?

An FLI below 30 rules out fatty liver (negative likelihood ratio ~0.2), and an FLI of 60 or higher rules it in (positive likelihood ratio ~4.3). Scores between 30 and 59 are indeterminate and do not confirm or exclude steatosis, so imaging or clinical judgment is required.

Which units must I use for the inputs?

The published formula uses triglycerides and GGT in the original derivation units: triglycerides in mg/dL and GGT in U/L, with BMI in kg/m² and waist circumference in cm. If your lab reports triglycerides in mmol/L, convert to mg/dL (multiply by 88.5) before applying the equation, or the score will be wrong.

Is the FLI reliable in lean or Asian patients?

Less so. Because BMI and waist circumference dominate the score, the standard cutoffs underperform in lean MASLD and in populations that develop fatty liver at lower BMI, including many East Asian cohorts. In these groups a normal FLI does not reliably exclude steatosis.

Can I use the FLI in someone who drinks heavily?

No. The FLI was developed to predict non-alcohol-related fatty liver, and GGT is confounded by alcohol. In patients with significant alcohol intake, cholestasis, or GGT-inducing drugs, the index is falsely elevated and should not be used to infer metabolic steatosis.

References

  • Bedogni G, Bellentani S, Miglioli L, Masutti F, Passalacqua M, Castiglione A, Tiribelli C. The Fatty Liver Index: a simple and accurate predictor of hepatic steatosis in the general population. BMC Gastroenterol. 2006;6:33. PMID: 17081293.
  • European Association for the Study of the Liver (EASL), European Association for the Study of Diabetes (EASD), European Association for the Study of Obesity (EASO). EASL-EASD-EASO Clinical Practice Guidelines on the Management of Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD). Obes Facts. 2024;17(4):374-444. PMID: 38852583.

Editorial review and citation methodology

Reviewed by the Quick Medical Calculator Editorial Team. Last reviewed: April 29, 2026. The review checks calculator inputs, intended population, interpretation, limitations, and source alignment.

  • Prefer original validation studies for scoring systems and prediction tools.
  • Use current specialty society guidance, transplant allocation policy, public health guidance, or regulator resources when they govern clinical use.
  • Include limitations and safety notes when a calculator is population-specific, context-dependent, or unsuitable as a standalone decision tool.

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