Health · 4 min read
Understanding Your BMI
What Body Mass Index measures, how to read the categories, and the limits of BMI as a health metric.
Try the bmi calculatorPut these numbers to workOpen →Body Mass Index (BMI) is a quick screening number that relates your weight to your height. It doesn't measure body fat directly, but for most people it gives a reasonable first indication of whether their weight sits in a healthy range.
The formula
Metric: BMI = weight (kg) ÷ height (m)². Imperial: BMI = 703 × weight (lb) ÷ height (in)².
The categories
- •Under 18.5 — underweight
- •18.5 to 24.9 — normal weight
- •25 to 29.9 — overweight
- •30 and above — obese
What BMI doesn't tell you
BMI uses only height and weight, so it can't tell muscle from fat or show where fat is stored. A muscular athlete may read as "overweight" while carrying very little fat, and two people with the same BMI can have very different health profiles. For a fuller picture, look at body-fat percentage and waist measurement alongside BMI.
BMI is a screening tool, not a diagnosis. For medical decisions, talk to a healthcare professional.
- 1Choose metric or imperial units.
- 2Enter your height and weight.
- 3Read your BMI, category and the healthy-weight range for your height.