Free, private calculators that help you understand common clinical measurements. Estimate APRI and FIB-4 liver fibrosis screening scores or calculate adult BMI.
Liver fibrosis assessment
APRI Calculator
Estimate the AST to Platelet Ratio Index using values from a blood test report.
Your values are calculated in this browser and are not sent to a server.
APRI score interpretation
APRI score
Interpretation
Likelihood of liver fibrosis
< 0.5
Minimal or no fibrosis
Low
0.5–1.5
Moderate fibrosis or significant fibrosis
Intermediate
> 1.5
Severe fibrosis or cirrhosis
High
Important: APRI is a screening estimate, not a diagnosis. Results are best interpreted by a qualified clinician alongside medical history, examination, imaging, and other tests. Published thresholds are primarily based on studies of people with hepatitis C.
Formula and clinical background reference: Hepatitis C Online, University of Washington. Source evidence includes Lin et al., Hepatology (2011), and Chou & Wasson, Annals of Internal Medicine (2013).
What is an APRI calculator?
APRI stands for AST to Platelet Ratio Index. It is a non-invasive calculation that combines an aspartate aminotransferase blood test result with platelet count. Clinicians may use APRI as one part of liver fibrosis assessment, especially in people with hepatitis C. It can help estimate risk, but it does not replace clinical evaluation, imaging, elastography, or other fibrosis tests.
How to use the APRI calculator
1. Enter AST: use the AST level shown on the blood test report in IU/L.
2. Enter the laboratory upper limit: use the AST upper limit of normal from the same report. If unavailable, 40 IU/L is commonly used in APRI studies.
3. Enter platelet count: use the result expressed in 10⁹/L.
Advanced fibrosis screening
FIB-4 Calculator
Estimate the Fibrosis-4 score using age and routine blood test results.
Formula
FIB-4 = (age × AST) ÷ (platelet count × √ALT)
Your FIB-4 score
Enter all four values to see the result.
Your values are calculated in this browser and are not sent to a server.
FIB-4 interpretation for advanced fibrosis
Below 1.45
Advanced fibrosis less likely
1.45–3.25
Indeterminate result
Above 3.25
Advanced fibrosis more likely
Important: FIB-4 is a screening estimate, not a diagnosis. The original thresholds were validated in adults with HIV/HCV coinfection, and performance can differ by age, condition, and population. A clinician should interpret the result with medical history and other fibrosis assessments.
The Fibrosis-4 score combines age, AST, ALT, and platelet count to estimate the likelihood of advanced liver fibrosis. It is a non-invasive screening calculation that can help clinicians decide whether additional fibrosis assessment may be appropriate.
How to use the FIB-4 calculator
1. Enter age: use the patient’s age in years.
2. Enter AST and ALT: use results from the same blood test in U/L.
3. Enter platelet count: use the result expressed in 10⁹/L.
Healthy weight screening
BMI Calculator
Calculate adult body mass index using metric or imperial measurements.
Your BMI
Enter your weight and height to see the result.
Your measurements stay on your device and are not stored or transmitted.
Adult BMI ranges
Below 18.5
Underweight
18.5–24.9
Healthy weight
25.0–29.9
Overweight
30.0 or above
Obesity range
BMI is a screening measure for adults, not a direct measurement of body fat or overall health. It may be less informative for children, pregnancy, older adults, and people with high muscle mass. Discuss weight or health concerns with a qualified clinician.
How the BMI calculator works
Body mass index compares weight with height to provide a general adult weight category. The metric formula is weight in kilograms divided by height in metres squared. The imperial formula multiplies weight in pounds by 703, then divides by height in inches squared.
BMI can be useful for population screening, but it does not measure body fat distribution, muscle mass, nutrition, or metabolic health. Waist measurement, medical history, laboratory results, and a clinician’s assessment can provide a more complete health picture.
Frequently asked questions
What is the APRI score?
The AST to Platelet Ratio Index is a non-invasive estimate that uses AST, the AST upper limit of normal, and platelet count to help assess the likelihood of liver fibrosis or cirrhosis.
How is APRI calculated?
Divide AST by the AST upper limit of normal, divide that result by platelet count in 10⁹/L, and multiply by 100.
How is FIB-4 calculated?
Multiply age by AST, then divide by platelet count multiplied by the square root of ALT. Scores below 1.45 and above 3.25 were used as lower and upper cutoffs in the original validation study.
What is a healthy BMI for adults?
For most adults, a BMI from 18.5 to 24.9 is generally classified as a healthy weight range. BMI is a screening measure, not a diagnosis.
Are my calculator values stored?
No. APRI, FIB-4, and BMI calculations happen in your browser. The values you enter are not submitted to or stored on a server.
