Nutrition
How to Calculate BMI and What It Really Means
How to calculate BMI with a worked example and an honest explanation of its limitations. When BMI is useful and when to ignore it.
BMI, or body mass index, is the most common quick check for whether weight is in a healthy range relative to height.
The formula is BMI equals weight in kilograms divided by height in meters squared.
Standard ranges: below 18.5 underweight, 18.5 to 24.9 normal, 25 to 29.9 overweight, 30 and above obese.
Where BMI breaks down: athletes with high muscle mass score as overweight. Older adults with low muscle can score as normal. It says nothing about fat distribution.
More useful numbers: starting BMI, current BMI, waist circumference, and weekly weight trend.