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BMI Calculator

Calculate your Body Mass Index and discover your health category. Free and no sign-up required.

Your BMI
<18.518.5-2525-30>30

What is BMI?

Body Mass Index (BMI) is a simple indicator used by the World Health Organization (WHO) to assess a person's body size. It is calculated by dividing weight (in kilograms) by the square of height (in meters). Developed by Belgian mathematician Adolphe Quetelet in the 19th century, BMI remains the most widely used screening tool in the world today.

BMI categories according to WHO

WHO defines four main categories: underweight (BMI below 18.5), normal weight (between 18.5 and 24.9), overweight (between 25 and 29.9) and obesity (30 and above). These thresholds were established from epidemiological studies showing a correlation between BMI and risks of cardiovascular disease, type 2 diabetes and certain cancers.

BMI and women's health: a direct link with the cycle

In women, weight plays a direct role in hormonal balance and the menstrual cycle. A BMI that is too low (below 18.5) can cause hypothalamic amenorrhea: the body, judging energy reserves to be insufficient, reduces estrogen production and suppresses ovulation. Conversely, a high BMI is associated with an increased risk of PCOS, irregular cycles and difficulty conceiving.

Limitations of BMI

BMI is a useful but imperfect indicator. It does not distinguish muscle mass from fat mass: a very muscular athlete may have a high BMI without being overweight. It also does not account for fat distribution. For a more complete assessment, other measurements such as waist circumference or bioelectrical impedance analysis can be useful as supplements.

Frequently Asked Questions

How do I calculate my BMI?
BMI is calculated by dividing your weight in kilograms by your height in meters squared: BMI = weight (kg) / height (m)^2. For example, for a person weighing 65 kg and 1.70m tall: BMI = 65 / (1.70 x 1.70) = 22.5. Our calculator does this calculation automatically.
What is the normal BMI for a woman?
A BMI between 18.5 and 24.9 is considered normal by WHO, regardless of sex. However, BMI does not account for body composition, age or body type. It is one of several indicators for assessing your health.
Is BMI reliable?
BMI is a simple and useful indicator for large-scale screening, but it has limitations. It does not distinguish fat mass from muscle mass and does not account for fat distribution. Athletes, elderly people and pregnant women are profiles for whom BMI alone is insufficient.
BMI and menstrual cycle: is there a link?
Yes, weight directly influences reproductive hormones. A very low BMI can cause amenorrhea (absence of periods) because the body lacks energy reserves. A high BMI can increase the risk of irregular cycles and PCOS. Maintaining a healthy weight is important for a regular cycle.

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