BMI Calculator
Enter your height and weight to calculate your BMI and see where it sits on the standard adult scale.
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How to use BMI Calculator
- Choose metric or imperial units.
- Enter your height and weight.
- Read your BMI and its category.
What BMI tells you
Body Mass Index compares weight to height to estimate whether someone is underweight, a healthy weight, overweight or obese. Doctors use it as a quick first screen because it is simple and needs no equipment. It is a starting point for a conversation, not a verdict on your health.
Adult BMI categories
- Below 18.5: underweight.
- 18.5–24.9: healthy weight.
- 25.0–29.9: overweight.
- 30.0 and above: obesity.
- These ranges apply to adults. Children and teens use age- and sex-specific percentile charts.
Limits of BMI
Because muscle weighs more than fat, a muscular person can have a high BMI without excess body fat. Older adults may have a healthy-looking BMI but low muscle. Waist measurement, body composition, blood pressure, cholesterol and lifestyle are all part of a fuller picture. For personal advice, speak with a doctor or registered dietitian.
Using the result sensibly
A single BMI figure is most useful when tracked over time or combined with other measurements. If your result is outside the healthy range, that is a prompt to look at the bigger picture rather than a diagnosis: diet, activity, waist size, family history and blood tests all matter more than one number.
Different countries and health bodies set slightly different thresholds for certain populations, and children, pregnant women and older adults need different interpretation. If you are worried about your weight, a doctor or registered dietitian can give advice that fits you.
Why use this bmi calculator tool
- Metric and imperial. cm/kg or feet-inches/pounds.
- WHO adult categories. Underweight, healthy, overweight, obesity.
- Private. Your measurements are never saved.
Frequently asked questions
What is the BMI formula?
BMI = weight in kg ÷ (height in metres)². A person 1.70 m tall weighing 70 kg has a BMI of 70 ÷ 2.89 ≈ 24.2.
What is a healthy BMI?
For most adults, 18.5 to 24.9 is classed as the healthy range. Some populations, including many South Asian groups, face higher health risks at lower BMI values, so local guidance may differ.
Is BMI accurate?
It is a rough screening tool. It ignores muscle mass, bone density, age and where fat is carried, so athletes can read as overweight. It does not diagnose anything.
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