What is BMI?
Body Mass Index compares your weight to your height: weight in kilograms divided by height in metres squared. The World Health Organization classes a BMI of 18.5–24.9 as normal, 25–29.9 as overweight and 30+ as obese. It is a population screening tool — fast, free and surprisingly well correlated with health outcomes at the population level.
How the calculator works
Enter weight and height in either imperial or metric units. The tool computes BMI, assigns the WHO category, and shows the body weight that would put you at the top of the healthy range (BMI 24.9) for your height.
Common use cases
- Insurance and annual health screening categories
- Tracking bulk and cut phases against population norms
- A quick sanity check alongside body-fat percentage
Formula & limits
BMI = kg / m². It cannot tell muscle from fat: a 220 lb bodybuilder and a sedentary man of the same height score identically. Pair BMI with the body-fat calculator or FFMI for a fuller picture, especially if you train seriously.
Frequently Asked Questions
Is BMI accurate for athletes?
Not for muscular athletes — muscle is denser than fat, so lifters routinely score 'overweight' at low body fat. Use FFMI or body fat percentage instead.
What BMI should I target?
The WHO healthy band is 18.5–24.9. The lowest all-cause mortality in large studies sits around 22–24.
Does the same scale apply to women?
Yes — the BMI cut-offs are identical for adult men and women.
Privacy & Your Data
StatPlay runs entirely in your browser. The numbers you enter never leave your device — there is no server, no account and no upload. We store only a single local preference flag when you dismiss the cookie notice.