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BMI calculator
Enter your height and weight to see your body mass index, the adult category it falls in and the healthy-weight range for your height. Everything is calculated in your browser.
GLPMate tracks weight and BMI over time — log a weigh-in or just tell the assistant your weight.
BMI is weight in kilograms divided by height in metres squared. For adults, a BMI under 18.5 is underweight, 18.5–24.9 is a healthy weight, 25–29.9 is overweight and 30 or more is obesity (WHO and CDC). It is a screening number, not a diagnosis: it can't tell muscle from fat, and it isn't used for children or during pregnancy.
How BMI is calculated
BMI = weight (kg) ÷ height (m)². With pounds and inches the formula is 703 × weight (lb) ÷ height (in)²; this calculator converts to metric first, so both give the same answer. The adult categories below are the ones used by the WHO and the US CDC.
| Category | BMI (kg/m²) |
|---|---|
| Underweight | < 18.5 |
| Healthy weight | 18.5–24.9 |
| Overweight | 25.0–29.9 |
| Obesity (class 1) | 30.0–34.9 |
| Obesity (class 2) | 35.0–39.9 |
| Obesity (class 3) | ≥ 40.0 |
What BMI can't tell you
BMI doesn't tell muscle from fat, so a very muscular person can score as overweight while carrying little fat, and an older adult can score as a healthy weight with little muscle. It also says nothing about where fat sits — waist size adds that information.
Who it isn't for
These categories are for adults. Children and teenagers are assessed with BMI-for-age percentiles instead, and BMI isn't used to judge weight during pregnancy.
Ethnicity and cut-offs
Health risks start at a lower BMI in some populations. A WHO expert consultation proposed lower action points for Asian populations (such as 23 and 27.5), and some national guidelines use them. Ask your clinician which cut-offs apply to you.
This calculator is for general education only. It is not medical advice or a diagnosis, and it doesn't decide whether any medicine is right for you — that is a conversation with your clinician.
Sources
- CDC adult BMI categories (the same cut-offs the WHO uses) — underweight, healthy weight, overweight and obesity classes 1–3
- WHO expert consultation on BMI in Asian populations (The Lancet, 2004) — lower public-health action points such as 23 and 27.5
- FDA prescribing information for Wegovy and Zepbound (Wegovy, Zepbound) — weight-management indications: obesity, or overweight with at least one weight-related condition
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BMI questions
What is a healthy BMI for adults?
For adults, the WHO and CDC class a BMI of 18.5 to 24.9 as a healthy weight. Below 18.5 is underweight, 25 to 29.9 is overweight and 30 or more is obesity, which is split into class 1 (30–34.9), class 2 (35–39.9) and class 3 (40 or more).
What BMI do you need for Wegovy or Zepbound?
Their labels cover adults with obesity, or with overweight plus at least one weight-related condition. In the trials behind them, that meant a BMI of 30 or more, or 27 or more with a condition such as high blood pressure, type 2 diabetes or high cholesterol. Insurance rules are often stricter, and only a clinician can prescribe.
Is BMI accurate if I am muscular?
Not very. BMI uses only height and weight, so it can label a muscular person as overweight. Waist circumference or a body-composition measurement gives a fuller picture, and your clinician can help you interpret them.
Does BMI work for Asian adults, children or pregnancy?
Health risks start at a lower BMI in Asian populations, so some guidelines use lower cut-offs. Children and teenagers are assessed with BMI-for-age percentiles instead of the adult categories, and BMI isn't used to judge weight during pregnancy.
Track the trend, not one number.
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