Body Mass Index (BMI) is calculated as weight in kilograms divided by height in meters squared, and the WHO healthy range is 18.5–24.9. Example: a person weighing 70 kg at 175 cm gets 70 ÷ 1.75² = a BMI of 22.9 — within the normal range.
How is it calculated?
The calculation has three steps: convert your height from centimeters to meters (175 cm = 1.75 m), square it (1.75² = 3.06), and divide your weight in kilograms by the result. The number is then compared to the WHO categories: under 18.5 underweight, 18.5–24.9 normal weight, 25–29.9 overweight, and 30 or above obesity. The same formula also gives the healthy weight range for any height — height squared × 18.5 up to height squared × 24.9.
Example: a person weighing 70 kg at 175 cm — 70 ÷ 3.06 = a BMI of 22.9, within the normal range, and the healthy weight range for that height is about 57–76 kg. Important caveats: BMI is a statistical screening measure, not a medical diagnosis — it does not distinguish muscle mass from fat (muscular athletes score high), and it is not suited to children and teens, pregnant women or the elderly, who have adjusted measures. Waist circumference and body composition are important complementary indicators.
Frequently asked questions
What is a normal BMI?
According to the World Health Organization, a BMI between 18.5 and 24.9 is considered normal weight for adults. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obesity. For example, a person 175 cm tall is in the normal range when weighing roughly 57–76 kg.
Is BMI accurate for athletes?
Not necessarily. The formula uses only weight and height and cannot distinguish muscle mass from fat, so athletes with high muscle mass can score a BMI of 25 or more without excess body fat. In such cases, body-fat percentage, body composition and waist circumference give a more accurate picture.
How do I calculate BMI manually?
Divide your weight in kilograms by your height in meters squared. Example: at 175 cm and 70 kg — 1.75 × 1.75 = 3.06, then 70 ÷ 3.06 = 22.9. Compare the result to the categories: 18.5–24.9 is the normal range.
What is a normal BMI for women and men?
On the World Health Organization (WHO) scale, the normal BMI range for adults is 18.5-24.9, and it is identical for men and women. Body composition does differ between the sexes — women typically have a higher body-fat percentage — but the screening scale itself does not change. A BMI of 22, for example, counts as normal for both a woman and a man.
How much should someone weigh at a height of 1.70 m?
At a height of 1.70 m, the weight range corresponding to a normal BMI (18.5-24.9) is roughly 53-72 kg. The calculation: 18.5 × 1.70² ≈ 53 kg at the low end and 24.9 × 1.70² ≈ 72 kg at the high end. Any weight within this range falls into the "normal" category of the BMI scale.
Is BMI suitable for children?
No. The standard BMI formula and the 18.5-24.9 scale apply to adults only. For children and teenagers, age- and sex-specific percentile growth charts are used instead, with tracking done at Tipat Halav (well-baby clinics) or by a pediatrician.
The information on this site is a general estimate for informational purposes only, is not medical advice and is no substitute for consulting a doctor. Your data is never stored.
