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Body Mass Index
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Enter your height and weight to calculate your BMI instantly. Interpret your result with a dietitian's perspective.

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What Is Body Mass Index (BMI)?

Body Mass Index (BMI) is a practical measurement method that indicates how healthy a person's weight is relative to their height. This formula was developed in 1832 by Belgian mathematician Adolphe Quetelet and is widely used by health professionals worldwide today.

BMI does not directly measure body fat; however, it provides a reliable starting point for assessing the risk of being overweight or obese. The World Health Organization (WHO) and many national health organizations recognize BMI as a standard tool for assessing nutritional status and health risks.

⚠ Important Note: BMI alone is not a complete indicator of your health. Factors such as muscle mass, bone density, age, and gender can influence the result. A dietitian consultation is recommended for a definitive assessment.

How Is Body Mass Index Calculated?

BMI calculation is based on a very simple formula:

BMI = Weight (kg) ÷ Height² (m²)

Example calculation: For a person who is 165 cm (1.65 m) tall and weighs 65 kg:

BMI = 65 ÷ (1.65 × 1.65) = 65 ÷ 2.7225 = 23.88

This value corresponds to the Normal Weight category.

What Should the Body Mass Index Be?

BMI categories established by the WHO for adults are as follows:

BMI RangeCategoryHealth Risk
Below 18.5UnderweightModerate risk
18.5 – 24.9✓ Normal WeightLow risk
25.0 – 29.9OverweightIncreased risk
30.0 – 34.9Obese (Class I)High risk
35.0 – 39.9Obese (Class II)Very high risk
40.0 and aboveMorbid Obesity (Class III)Extremely high risk

Body Mass Index (BMI) for Women

The BMI calculation formula is the same for women and men; however, ideal BMI values and their interpretation should be evaluated considering gender. Women naturally have a higher body fat percentage compared to men; therefore, the same BMI value may indicate different health risks in women and men.

♀ For Women
  • Normal BMI range: 18.5 – 24.9
  • BMI varies during pregnancy
  • Fat distribution may change after menopause
  • Hormonal conditions like PCOS affect BMI
♂ For Men
  • Normal BMI range: 18.5 – 24.9
  • BMI can be misleading for those with high muscle mass
  • Abdominal obesity should be assessed separately
  • Should be interpreted alongside waist circumference

BMI Calculation for Children

The BMI calculation formula for children is the same as for adults, but interpretation is different. Since children are in a growth phase, BMI is evaluated using percentile curves determined by age and gender.

Percentile RangeCategory
Below 5th percentileUnderweight
5th – 84th percentile✓ Healthy Weight
85th – 94th percentileOverweight
95th percentile and aboveObese
👶 Important: For children under 2 years of age, weight-for-length curves are used instead of BMI. Always evaluate your child's weight status with a pediatrician or pediatric dietitian.

Frequently Asked Questions

Does BMI fully show my health status?+
BMI is a general screening tool and is not a complete reflection of your health on its own. Athletes with high muscle mass may show a high BMI value even though they are actually healthy. A complete evaluation requires additional measurements such as waist circumference, body fat percentage, and blood values.
What should the ideal BMI value be?+
The ideal BMI range for adults is between 18.5 and 24.9. However, being within this range does not automatically mean you are healthy. Nutrition quality, level of physical activity, and blood values should also be considered.
Why do I feel overweight even though my BMI is normal?+
This condition can be called "hidden obesity" or "normal weight metabolic obesity." Even if BMI is within normal limits, body fat percentage may be high and muscle mass may be low. Your body composition can be evaluated in more detail with methods such as bioimpedance analysis or DEXA.
What units are used in BMI calculation?+
In BMI calculation, weight is used in kilograms (kg) and height in meters (m). The height value is squared in the calculation. For example, for 170 cm, 1.70² = 2.89 is used.
Is BMI calculation valid during pregnancy?+
Since body weight changes rapidly during pregnancy, standard BMI calculation does not provide a valid indicator. The pre-pregnancy BMI value is used as the basis for determining the amount of weight to be gained during pregnancy. It is strongly recommended to work with a dietitian regarding nutrition during pregnancy.
Is calculating BMI without seeing a dietitian sufficient?+
Calculating BMI is a good starting point. However, dietitian consultation is required for correct interpretation of the result, evaluation of individual risk factors, and creation of a personalized nutrition plan. Expert support is especially important for individuals whose BMI falls outside the normal range.

Is Your BMI Outside Normal Range?

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