BMI Calculator
Your Body Mass Index
Note: BMI is for guidance only and does not account for individual body composition.
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Body Mass Index (BMI) explained simply
Body Mass Index (BMI) is the best-known guide for relating body weight to height. With a BMI calculator you can find your weight category in seconds – using the widely adopted WHO classification. The value does not replace medical advice, but it helps with initial orientation and tracking changes over time.
BMI has been used for decades in medicine, prevention, and health apps because it is easy to calculate and compare. For adults, the further the value moves away from the normal range, the higher the statistical risk of related conditions. At the same time, muscle mass, age, and body shape matter – so always interpret the result in context.
Calculate BMI – formula and input
The BMI formula is: body weight in kilograms divided by height in metres squared (kg/m²). In the calculator you enter height in centimetres and weight in kilograms – the tool handles conversion automatically. Example: 175 cm and 70 kg give a BMI of about 22.9. You see the value instantly with the matching category: underweight, normal weight, overweight, or obesity.
BMI categories according to WHO
The World Health Organization defines for adults: below 18.5 underweight, 18.5 to 24.9 normal weight, 25 to 29.9 overweight, and 30 or above obesity. These thresholds are reference values for people aged 18 to 65. Separate charts apply for children, pregnant women, and older adults.
Important: BMI does not reflect body fat percentage, muscle mass, or bone density. Athletic people may have a high BMI despite low body fat. Use the calculator for orientation – and seek medical advice for health decisions.
ToolkitOne BMI calculator – free online
Our BMI calculator is free, privacy-friendly, and usable without sign-up. All calculations run locally in your browser. With Comfort Login you can save results and compare your history – useful for conscious weight tracking. Enter height and weight, click calculate, and get your Body Mass Index with category instantly. Use the BMI calculator regularly, realistically, and as part of a broader picture of health.