Fatty liver — the buildup of fat inside liver cells, medically called hepatic steatosis — is one of the most common chronic liver conditions in the world, yet it usually produces no symptoms at all. Most people discover it by accident on a blood test or an ultrasound. This liver fat calculator estimates your Fatty Liver Index (FLI), a validated score built by Giorgio Bedogni and colleagues from four routine measurements you almost certainly already have: your BMI, your waist circumference, your GGT level, and your triglyceride level.
The FLI is not an ultrasound and it is not a diagnosis. It is a probability: a number from 0 to 100 that estimates how likely it is that imaging would show extra fat in your liver. When the score is low, fatty liver is unlikely; when it is high, it is worth bringing the result to your doctor. Enter your four numbers below and the score updates instantly.
How to Use
- Enter your Body Mass Index (BMI). If you do not know it, divide your weight in kilograms by your height in meters squared — for example, 180 lb and 5 ft 9 in works out to about 26.6.
- Measure your Waist Circumference at the level of your belly button, keeping the tape snug but not compressing the skin. Enter it in inches. If your clinic used centimeters, divide by 2.54 first.
- Type your GGT (gamma-glutamyl transferase) from a recent blood test, in units per liter (U/L). GGT is the liver enzyme that tends to rise earliest with fat and alcohol.
- Enter your Triglycerides from your lipid panel, in mg/dL. Use a fasting value if you have it.
- Read the result card. Your Fatty Liver Index appears as a percentage, followed by a risk category: Low (under 30%), Intermediate (30% to 60%), or High (over 60%).
Because the formula takes the natural logarithm of triglycerides and GGT, both values must be positive numbers. A non-positive or negative entry is rejected rather than producing a meaningless score.
The Fatty Liver Index Formula
The FLI comes from Bedogni's 2006 derivation on a large general-population sample. The math is a logistic model — the same shape that converts a raw score into a 0-to-100% probability:
FLI = 100 × e^L / (1 + e^L)
where
L = 0.953 × ln(Triglycerides) + 0.139 × BMI + 0.718 × ln(GGT) + 0.053 × Waist_cm − 14.788
Waist circumference must be in centimeters in the formula, so the calculator multiplies your waist-inches by 2.54 behind the scenes. Triglycerides are in mg/dL and GGT in U/L, matching the units the score was trained on.
A worked example: BMI 30, waist 40 in (101.6 cm), GGT 60 U/L, triglycerides 200 mg/dL. The four terms contribute roughly 5.05, 4.17, 2.94 and 5.39, giving L ≈ 2.76. Plugging into the logistic curve gives FLI ≈ 94%, which falls firmly in the High band. That is the expected result for someone with obesity, a large waist and elevated liver enzymes and lipids.
How the Risk Bands Work
The FLI uses three clinically recognized bands:
- Low (FLI under 30%) — hepatic steatosis is unlikely. In validation studies an FLI below 30 has a high sensitivity for ruling out fatty liver, so a low score is reassuring.
- Intermediate (30% to 60%) — the result is uncertain. Many people in this band do have some fat in the liver, but the score alone cannot decide; this is where lifestyle change and repeat testing matter.
- High (over 60%) — fatty liver is likely. An FLI above 60 has a high specificity for ruling in steatosis and should prompt a conversation with a clinician about liver enzymes, fibrosis assessment, weight and metabolic health.
The score is driven most strongly by waist circumference and triglycerides, which is why central obesity and elevated blood fats are the two levers you can move fastest.
Examples
Example 1 — A metabolically healthy adult. BMI 22, waist 30 in, GGT 15 U/L, triglycerides 90 mg/dL. The four terms are small, L is negative, and the result is FLI ≈ 19% — Low. This person is very unlikely to have detectable fatty liver.
Example 2 — The high-risk profile. BMI 30, waist 40 in, GGT 60 U/L, triglycerides 200 mg/dL. As worked above, the score lands near 94% — High. Even though this person may feel completely well, the probability of ultrasound-detected steatosis is very high and a medical follow-up is appropriate.
Example 3 — The uncertain middle. BMI 26, waist 35 in, GGT 30 U/L, triglycerides 120 mg/dL. The calculation gives FLI ≈ 63% — just inside the High band, close to the boundary. A few pounds of waist loss and lower triglycerides would pull the score back under 60%, which illustrates how sensitive the result is to the modifiable factors.
FAQ
What is a normal Fatty Liver Index?
A normal or reassuring FLI is anything under 30%. The score ranges from 0 to 100%; below 30 makes fatty liver unlikely, 30 to 60 is uncertain, and above 60 makes fatty liver likely. There is no single "perfect" number — the bands are what matter.
How accurate is the liver fat calculator?
The FLI was validated against ultrasound-measured hepatic steatosis and is widely used in population studies. It is a screening probability, not a diagnostic test; it correlates well with imaging but cannot replace an ultrasound, FibroScan, or a clinician's assessment, and it does not measure liver inflammation or fibrosis directly.
Can I get a low FLI and still have fatty liver?
Yes. A low score makes fatty liver unlikely but does not completely exclude it, especially in people who are lean but metabolically unhealthy. Conversely, a high score does not prove steatosis. The FLI is best used to decide whether further testing is worth pursuing.
Which lab values do I need?
You need four numbers: your BMI (or height and weight), your waist circumference in inches, your GGT in U/L from a liver panel, and your fasting triglycerides in mg/dL from a lipid panel. All four appear on routine blood workups.
Does alcohol affect the Fatty Liver Index?
The FLI itself does not ask about alcohol directly, but GGT and triglycerides both rise with alcohol use, so heavy drinking will inflate the score. If your GGT is high mainly because of alcohol, reducing drinking is one of the most effective ways to bring both the enzymes and the liver fat down.
Can I lower my FLI?
Yes. Because the score tracks waist size, BMI, triglycerides and GGT, the same interventions that improve metabolic health also lower it: gradual weight loss (even 5% of body weight), cutting refined sugars and ultra-processed foods, regular exercise, limiting alcohol, and treating elevated triglycerides. A lower waist and lower triglycerides move the score more than any other single change.
Disclaimer
This liver fat calculator is provided for informational purposes only and is not medical advice, diagnosis, or treatment. The Fatty Liver Index is an estimated probability derived from the Bedogni formula and your self-entered numbers; it is not a substitute for a clinical examination, blood work review, imaging, or the judgment of a licensed healthcare provider. Do not start, stop, or change any medication or treatment based on this result. If you are concerned about your liver health, have abnormal liver tests, or your score falls in the High range, please consult a qualified physician.