NAFLD Fibrosis Score (NFS) Calculator
Estimate the likelihood of advanced liver fibrosis (stage F3–F4) in non-alcoholic / metabolic fatty liver disease (NAFLD/MASLD) with the NAFLD Fibrosis Score — a non-invasive score from age, BMI, the AST/ALT ratio, platelet count, albumin and whether impaired fasting glucose or diabetes is present. It helps decide who can be reassured and who needs further assessment such as elastography.
About the NAFLD Fibrosis Score
The NFS is a non-invasive estimate of advanced fibrosis in NAFLD/MASLD, built from routine measurements plus BMI and diabetes status. It is a first-line triage test, often used with FIB-4 and elastography. Source: Angulo P et al., Hepatology 2007;45(4):846–854.
Frequently asked questions
What is the NAFLD Fibrosis Score formula?
NFS = −1.675 + 0.037 × age (years) + 0.094 × BMI (kg/m²) + 1.13 × (impaired fasting glucose or diabetes: yes = 1, no = 0) + 0.99 × (AST ÷ ALT) − 0.013 × platelet count (×10⁹/L) − 0.66 × albumin (g/dL). AST and ALT are in U/L; only their ratio matters. Every term is a routine clinic or laboratory value, which is what makes the score usable without imaging or biopsy. As a worked example, an age of 55, BMI 32, diabetes present, an AST/ALT ratio of 0.9, platelets of 180 ×10⁹/L and albumin of 4.0 g/dL give a score of about 0.41.
What do the NFS results mean?
The NAFLD Fibrosis Score uses two cut-offs. Below −1.455, advanced fibrosis is unlikely (F0–F2) with a high negative predictive value, so many people can be reassured. Above 0.676, advanced fibrosis (F3–F4) is likely and referral for further assessment is warranted. Between −1.455 and 0.676 is indeterminate, usually prompting a second test such as elastography.
What albumin unit should I use?
The formula uses albumin in g/dL (for example 4.0). If your lab reports albumin in g/L (common outside the US, for example 40), switch the unit selector and the calculator converts it (g/L ÷ 10 = g/dL). Platelets are entered in ×10⁹/L, the same number as ×10³/µL.
How does the NFS differ from FIB-4?
The NFS and FIB-4 are both non-invasive fibrosis scores for fatty liver disease and are often used together. FIB-4 needs only age, AST, ALT and platelets; the NAFLD Fibrosis Score adds BMI, albumin and diabetes status, so it captures more metabolic context. Many pathways use FIB-4 first and the NFS (or elastography) as a second step for indeterminate results.
Can the NFS replace a liver biopsy?
The NAFLD Fibrosis Score does not replace a liver biopsy. It estimates the probability of advanced fibrosis rather than staging it precisely, and its accuracy falls at extremes of BMI and in older patients, where the lower cut-off yields more false positives. It is a triage tool used with elastography, imaging and clinical judgement, not a diagnosis. This calculator is an educational reference, not medical advice.
This is a reference tool, not a diagnosis or medical advice. Results depend on the laboratory, assay and clinical context, and reference intervals vary between labs and by age and sex — always read your result against the range printed on your own report and discuss it with a qualified healthcare professional.
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