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BMI & Body Fat Estimator
Body Mass Index and body fat percentage from standard formulas.
How it works
Body Mass Index divides your weight in kilograms by the square of your height in metres. It is a screening tool, not a diagnosis, and it works best as a first check alongside waist size, fitness and how you actually feel. Body fat here is estimated with the Deurenberg formula, which combines BMI with age and sex, because two people with the same BMI can carry quite different amounts of fat. The result is useful for tracking a trend over months, even though it cannot match a DEXA scan or skinfold test for precision.
How to read the result
A BMI from 18.5 to 24.9 is classed as the healthy range, 25 to 29.9 as overweight, and 30 or above as the obesity range, with below 18.5 classed as underweight. Treat a single number cautiously: athletes, older adults and people with high muscle mass are the classic cases where BMI misleads. If your BMI is high but your waist is trim and you train regularly, body composition matters more than the index alone.
One practical tip
Weigh yourself at the same time of day, once a week, and record the trend rather than reacting to daily swings. Water, meals and clothing can shift the scale by a kilogram or more, while a steady four-week direction tells you whether a habit change is actually working.
If your BMI sits near a category boundary, a small change in either direction can move the label without changing your health much, which is another reason to judge progress by measurements, fitness and blood markers together rather than by a single threshold.