About BMI Logic

BMI Logic started when a fit, muscular guy in his 50s plugged his numbers into a standard BMI chart and got told he was "obese." The formula behind BMI dates to the 1830s and only knows two things: your height and your weight. It can't see muscle, frame, age, or where you carry your weight.

So we built a smarter version. BMI Logic keeps standard BMI, because your doctor still uses it, and adds the measurements researchers use to see what BMI misses: waist-to-height ratio, estimated body fat, Fat Mass Index, FFMI, an age-aware view, and frame size. Every formula is published and cited on our How it works page.

Free and private

No sign-up, no tracking of your numbers. The calculator runs entirely in your browser, and nothing you type is sent to a server.

Not medical advice

BMI Logic is an educational screening tool for adults. Talk with your doctor about your health, and bring your results along if they help the conversation.

Contact

Questions or ideas? Email hello@bmilogic.com.