Free BMI calculator: enter height, weight, age and sex to get your body mass index and weight category on both the WHO and Asia-Pacific scales. Adults and children 2–19 (BMI-for-age percentile).
Enter your height and weight to get your body mass index, your weight category on both the WHO and Asia-Pacific scales, and — for ages 2–19 — a CDC BMI-for-age percentile. Then turn the number into a balanced plate.
Body mass index (BMI) is your weight in kilograms divided by the square of your height in metres. It's a quick, equipment-free screen for whether your weight is in a healthy range for your height — the same number the World Health Organization and most public-health bodies use to compare populations.
BMI is a screening tool, not a diagnosis, and it can't tell muscle from fat. A muscular athlete and a sedentary person can share a BMI with very different body composition, which is why a high reading is a prompt to look closer — with a body-fat estimate, waist measurement, or a clinician — rather than a verdict on its own.
On the WHO international scale, a BMI under 18.5 is underweight, 18.5–24.9 is a healthy weight, 25–29.9 is overweight, and 30 or above is obesity (split into classes I, II and III at 30, 35 and 40).
The Asia-Pacific criteria shift the overweight and obesity lines down to 23 and 25. They're the standard the Korean Society for the Study of Obesity uses, because research — summarized by a WHO Expert Consultation in the Lancet in 2004 — shows that Asian populations, including Koreans, develop type 2 diabetes and cardiovascular disease at a lower BMI than European populations. The calculator shows both so you can see exactly where your number falls on each.
For anyone aged 2 to 19, a single fixed cutoff doesn't work, because healthy BMI changes with age and differs between boys and girls. Instead, BMI is plotted on the CDC growth reference as a percentile — how the child compares with others of the same age and sex.
Below the 5th percentile is underweight, 5th–84th is a healthy weight, 85th–94th is overweight, and 95th or above is obesity (with a severe-obesity band above 120% of the 95th percentile). Korea uses the same percentile approach for children. These are screening bands; a pediatric provider is the right place to interpret a child's growth.
If your BMI sits outside the healthy range, small sustained changes move it more reliably than crash diets: a balanced plate, enough protein, regular activity, and — if you're aiming to lose — a modest calorie deficit. Our calorie-deficit calculator estimates a sensible target, and the MyPlate Plan turns it into daily food-group amounts.
And if your BMI is in the healthy range but you carry a lot of muscle or a large waist, trust the fuller picture over the single number. BMI is the starting point, not the finish line.
Body mass index
W = weight in kilograms, H = height in metres. Imperial equivalent: BMI = 703 × weight(lb) ÷ height(in)². The result is rounded to one decimal place.
BMI-for-age percentile — LMS z-score (ages 2–19)
L, M, S are the CDC BMI-for-age reference parameters (skewness, median, coefficient of variation) for the child's exact age and sex; the z-score converts to a percentile. Above the 95th percentile the CDC 2022 extended-percentile model is used.
WHO international vs. Asia-Pacific / KSSO. Ages 2–19 use BMI-for-age percentiles instead.
| Category | WHO · Asia-Pacific |
|---|---|
| Underweight | <18.5 · <18.5 |
| Healthy weight | 18.5–24.9 · 18.5–22.9 |
| Overweight | 25.0–29.9 · 23.0–24.9 |
| Obesity | ≥30 · ≥25 |
BMI is your weight in kilograms divided by your height in metres squared (kg/m²). In imperial units it's weight in pounds ÷ height in inches², × 703. This calculator does the conversion for you either way.
On the WHO scale, a healthy weight is a BMI of 18.5–24.9. On the Asia-Pacific scale used in Korea, the healthy range is 18.5–22.9, because overweight is defined from 23. This page shows your number on both.
Because health risk starts at a lower BMI. A WHO Expert Consultation (Lancet, 2004) and the Korean Society for the Study of Obesity found that type 2 diabetes and cardiovascular disease appear at a lower BMI in Asian populations, so overweight is set at 23 and obesity at 25 rather than the WHO 25 and 30.
BMI is a good population screen but a rough individual measure — it can't distinguish muscle from fat or show where fat sits. Very muscular people can read high while lean; older adults can read 'healthy' while carrying excess fat. Pair BMI with a waist measurement or body-fat estimate for a fuller read.
For ages 2–19, BMI is compared with a CDC growth chart for the child's exact age and sex and reported as a percentile, not against adult cutoffs. Under age 2, BMI isn't used at all — a weight-for-length chart is used instead.
Yes, if it's driven by excess fat: a balanced plate, enough protein, regular activity and a modest calorie deficit lower weight gradually. Estimate a sensible deficit on our calorie-deficit calculator and turn it into a plan with the MyPlate Plan calculator.