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BMI Calculator

Body mass index (BMI) compares your weight to your height to place you in a broad weight category. This BMI calculator divides your weight in kilograms by the square of your height in metres and reports the standard adult ranges: under 18.5 (underweight), 18.5–24.9 (normal), 25–29.9 (overweight), and 30 or above (obese). BMI is a quick population-level screen, not a measure of body fat or health — it does not distinguish muscle from fat and can misclassify athletes, older adults, and some ethnic groups.

Calculate

Default result: 24.6

BMI Calculator · Result

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Body mass index

24.6

176 lb × 70.9 in

24.6

This calculator provides general estimates for educational purposes only and is not medical advice. Results are based on population formulas and may not reflect your individual circumstances. Consult a qualified healthcare professional before making changes to your diet, exercise, or health routine.

Reviewed by the calculators.dev team · Last updated 2026-06-23

Formula reviewed against World Health Organization — Body mass index (BMI) classification (Quetelet index)

How to calculate

Enter your weight and height in whichever units you prefer; the calculator converts them and divides weight (kg) by height (m) squared. For 80 kg and 1.80 m that is 80 ÷ 3.24 = 24.7. Compare the number against the adult ranges shown above. Because BMI uses only height and weight, treat it as a starting point and pair it with other measures (waist size, body-fat estimate, or a clinician's assessment) rather than a verdict on health.

BMI = weight_kg ÷ (height_m)². In imperial units the equivalent is BMI = 703 × weight_lb ÷ (height_in)². Variables: weight is body mass and height is standing height. The result is in kg/m². The cut-points (18.5, 25, 30) are the standard adult thresholds defined by the WHO; they are the same for men and women but are not age- or muscle-adjusted.
Example calculation

Someone who weighs 80 kg (about 176 lb) and is 1.80 m tall (about 5 ft 11 in) has a BMI of 80 ÷ (1.80 × 1.80) = 80 ÷ 3.24 = 24.7, which falls in the standard “normal weight” range (18.5–24.9).

bmi
24.7

Assumptions

  • BMI is calculated for adults using the standard WHO adult cut-points; children and teens use age- and sex-specific percentile charts instead.
  • BMI estimates weight relative to height only — it does not measure body-fat percentage and cannot tell muscle from fat.
  • The categories are population screens, so a single BMI number is not a diagnosis of health or disease.

Common mistakes

  • Reading BMI as a body-fat percentage. A muscular athlete can have a high BMI with low body fat, and a sedentary person can have a “normal” BMI with high fat.
  • Using adult cut-points for a child or teenager, who should be assessed on age- and sex-specific BMI-for-age percentiles.
  • Mixing units — entering height in centimetres but reading it as metres, which makes the BMI a hundred times too small or large.

Frequently asked questions

What is a healthy BMI range?

For most adults the WHO defines 18.5 to 24.9 as the normal range, 25 to 29.9 as overweight, and 30 or above as obese. These are screening bands, not strict health limits.

Is BMI accurate for athletes?

Not very. BMI counts muscle the same as fat, so a lean, muscular athlete can land in the overweight or obese band despite low body fat. Use a body-fat estimate or waist measurement alongside it.

Does BMI work the same for men and women?

The formula and cut-points are identical for adult men and women. Body-fat percentage differs between the sexes at the same BMI, which is one reason BMI is only a rough screen.

Why is BMI only an estimate?

It uses just height and weight, ignoring muscle, bone density, fat distribution, age, and ethnicity. It is useful for population trends but should not be the only measure of an individual's health.

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