Fatty Liver Index (FLI) Calculator
Fatty Liver Index (FLI) Calculator
Estimate the probability of hepatic steatosis from BMI, waist circumference, triglycerides and GGT — no imaging required.
Fatty Liver Index (FLI)
4 inputs → 0–100BMI 30, waist 102 cm, triglycerides 180 mg/dL, GGT 55 U/L
Formula
FLI = [ eʸ ÷ (1 + eʸ) ] × 100
- triglycerides
- mg/dL — multiply mmol/L by 88.6
- BMI
- kg/m²
- GGT
- U/L
- waist
- cm, measured at the midpoint between the lowest rib and the iliac crest
Worked example
BMI 30, waist 102 cm, triglycerides 180 mg/dL, GGT 55 U/L
y = 0.953×ln(180) + 0.139×30 + 0.718×ln(55) + 0.053×102 − 15.745
y = 4.951 + 4.170 + 2.877 + 5.406 − 15.745 = 1.659
FLI = e^1.659 ÷ (1 + e^1.659) × 100 = 84.0
Thresholds
| FLI | Interpretation | Likelihood ratio |
|---|---|---|
| < 30 | Steatosis ruled out | LR− ≈ 0.2 |
| 30 – 60 | Indeterminate | — |
| ≥ 60 | Steatosis ruled in | LR+ ≈ 4.3 |
What the index does and does not tell you
The fatty liver index was derived against ultrasound in a general population cohort and gives a probability of hepatic steatosis from four routinely available measurements. It is used mostly in epidemiology and in primary care case-finding, where imaging every at-risk patient is impractical.
Its most important limitation is what it measures. Steatosis is common — a quarter of adults or more — and on its own it is a weak predictor of liver outcomes. Fibrosis stage is what determines whether a patient develops cirrhosis, hepatocellular carcinoma or liver-related death. A high fatty liver index is therefore the beginning of an assessment, not its conclusion, and should be followed by FIB-4 or another fibrosis index rather than treated as a diagnosis.
Two of its four inputs are also strongly driven by adiposity, so the index is close to a composite obesity measure and performs less well in lean patients with metabolic fatty liver — a group increasingly recognised and one where it can produce a falsely reassuring result. Waist circumference measurement is also poorly standardised in practice, which adds noise.
Frequently asked questions
What is a normal fatty liver index?
Below 30 rules out hepatic steatosis with reasonable confidence. Above 60 rules it in. Between the two the index cannot classify the patient.
Which triglyceride units does it use?
mg/dL. Multiply an mmol/L value by 88.6 first — a triglyceride of 2.0 mmol/L is 177 mg/dL.
Does a high FLI mean liver damage?
No. It estimates fat in the liver, not scarring. Fibrosis stage determines outcome, so follow a high index with FIB-4 or elastography.
Can the index miss fatty liver in lean people?
Yes. BMI and waist circumference dominate the calculation, so lean metabolic fatty liver is under-detected. Clinical suspicion should override a low index in that group.
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References
- Bedogni G et al. The Fatty Liver Index: a simple and accurate predictor of hepatic steatosis in the general population. BMC Gastroenterol. 2006;6:33.
- EASL-EASD-EASO Clinical Practice Guidelines on the management of MASLD.