BMI Calculator

The BMI calculator computes your body mass index – the ratio of weight to height that shows how closely your weight matches the norm. Enter your height, weight and gender – the calculator shows your BMI, the WHO weight category, the ideal weight range for your height and how much you need to lose or gain to reach it.

What is BMI and why it matters

Body mass index is the simplest indicator every adult should keep an eye on. It answers a basic question: is my current weight harming my health? A high BMI is statistically linked to a higher risk of heart disease, type 2 diabetes and high blood pressure. A low BMI goes with a weaker immune system, vitamin deficiencies and hormonal problems. People whose BMI stays within the normal range live longer on average and get sick less often. BMI is a starting point: it shows whether you have a reason to change your lifestyle and lets you track progress through a diet or fitness program.

How to use the calculator

Enter your height in centimeters and your weight in kilograms, and choose your gender – the figure on the results panel changes accordingly. The calculator shows your BMI and the WHO category. Next to your current figure there is a dashed "goal" figure – the ideal weight range for your height (BMI 18.5–24.9). The pill below the figures tells you how much to lose or gain to reach the norm, and the marker on the scale shows where you sit between underweight and obesity.

BMI formula

BMI is calculated with the Quetelet formula: BMI = weight (kg) / height (m)². For example, at 70 kg and 175 cm: BMI = 70 / (1.75 × 1.75) = 22.9 – a normal value. The formula is simple but has limits: it does not account for gender, age or the muscle-to-fat ratio.

BMI	Category
16 −	Severe underweight
16–18,5	Underweight
18,5–25	Normal weight
25–30	Overweight (pre-obesity)
30–35	Obesity class I
35–40	Obesity class II
40 +	Obesity class III (morbid)

Limitations of BMI

BMI is a screening tool, not a diagnosis. It can overestimate body fat in athletes and muscular people (muscle is denser than fat), and it does not apply to pregnant or breastfeeding women. Children and teenagers have different norms that depend on age, and in older adults a slightly elevated BMI is less risky than in younger people. BMI also says nothing about fat distribution: dangerous visceral fat around the waist can exist even at a normal index. If your BMI is far from the norm, see a doctor instead of relying on the calculator alone.

This calculation is for information only and is not medical advice. If your BMI deviates from the norm, consult a doctor.

Частые вопросы

What is BMI?

BMI (body mass index) is the ratio of weight to the square of height. It quickly shows whether your weight is in the normal range: below 18.5 is underweight, 18.5–25 is normal, above 25 is overweight or obesity.

What BMI is considered normal?

By the WHO classification, a normal BMI is 18.5 to 25. A healthy optimal range is often quoted as 18.5–23. People with a BMI in the normal range have a lower risk of cardiovascular disease and type 2 diabetes on average.

How do I lower my BMI?

Through gradual weight loss: a moderate calorie deficit of 300–500 kcal a day, at least 150 minutes of activity per week and enough sleep. The calculator shows how many kilograms separate you from the upper bound of the norm – spread that journey over weeks, not days.

Why can an athlete have a high BMI?

Because BMI does not distinguish muscle from fat: muscle tissue is denser, so people with developed muscularity may get an "overweight" index without excess fat. For athletes, body composition measurements and waist circumference are more informative.

Does BMI apply to children and pregnant women?

No. The standard BMI scale is designed for adults aged 18–65. For children and teenagers, norms depend on age and gender and are assessed with percentile tables, while weight gain during pregnancy is a natural process guided by a doctor.

How often should I measure my BMI?

Once every 1–2 months is enough, at the same time of day under similar conditions. Weighing yourself too often reflects water fluctuations, not real changes in body fat. Regular checks help you notice a drift early, while it is still small.