How do you calculate your BMI?
To calculate your BMI, divide your weight in kilograms by your height in meters squared. The formula is: BMI = weight (kg) / height² (m²). For adults, a BMI between 18.5 and 24.9 is generally considered a normal weight range.
Good to know :
This answer helps you understand a topic or make an estimate, but it is not a substitute for professional advice. For any important decision regarding your health, finances, rights, safety or administrative procedures, please consult an official source or a qualified specialist.
Explanation
Body Mass Index, or BMI, estimates adult weight status using two simple values: weight and height. It is mainly used as a quick screening indicator to place a person in an underweight, normal weight, overweight or obesity range.
BMI is only a general indicator. It does not directly measure body fat, does not distinguish muscle from fat and does not show how weight is distributed. A very muscular athlete may therefore have a high BMI without having excess body fat. Conversely, someone with a “normal” BMI may still have other health risk factors.
For a more reliable interpretation, BMI can be combined with waist circumference, age, sex, overall health status and medical advice when needed.
Formula / method
BMI = weight (kg) / height (m)²
Typical adult interpretation:
- below 18.5: underweight;
- 18.5 to 24.9: generally normal weight;
- 25 to 29.9: overweight;
- 30 or more: obesity.
Concrete example
For a person weighing 70 kg and measuring 1.75 m:
BMI = 70 / (1.75 × 1.75)
BMI = 70 / 3.0625
BMI = 22.86
The result is therefore about 22.9, which falls within the range generally considered normal for adults.
Common mistake
A common mistake is entering height in centimeters in the formula. For 1.75 m, you must divide by 1.75², not by 175². Also remember that BMI is a screening indicator, not a medical diagnosis. It is not suitable on its own for children, pregnant women, frail older adults or very muscular people.
Sources & methodology
- World Health Organization — Obesity and overweight: BMI definition, adult thresholds for overweight and obesity, and reminder that BMI is a surrogate marker of fatness.
- CDC — Adult BMI Categories: adult BMI categories and common interpretation thresholds.
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