BMI Calculator
Check your Body Mass Index and see your healthy weight range.
How BMI works
The Body Mass Index (BMI) is defined as weight in kilograms divided by height in metres squared: BMI = kg / m². It is a screening tool used by the World Health Organization to categorise adults into underweight, healthy weight, overweight and obesity ranges. BMI does not distinguish between muscle and fat and should not be used alone to assess health; consider waist circumference, body composition and lifestyle.
The formula
BMI = weight (kg) / height (m)². Healthy range: 18.5 to 24.9.
Frequently asked questions
What is BMI and how is it calculated?
Body Mass Index is calculated by dividing your weight in kilograms by the square of your height in metres (BMI = kg / m²). It's a quick screening tool recommended by the World Health Organization.
What BMI range is considered healthy?
For an adult, a BMI between 18.5 and 24.9 is generally considered a healthy weight. Below 18.5 is classed as underweight, and above 25 as overweight, then obesity at higher levels.
Is BMI reliable for everyone?
No. It doesn't distinguish muscle mass from fat mass and can be misleading for very muscular athletes, older adults or pregnant women; it should be combined with other indicators such as waist circumference or body composition.
How does the calculator work out my healthy weight range?
It calculates the weights corresponding to the 18.5 and 24.9 BMI thresholds for your current height, giving you a target weight range in kilograms to stay within the 'healthy weight' category.
Can I use imperial units (pounds, feet/inches)?
Yes, a unit switch lets you toggle between metric (cm, kg) and imperial (ft/in, lb); the calculation adjusts automatically to your choice.
What should I do if my BMI is outside the healthy range?
A BMI outside the healthy range is just a starting point: talk to a healthcare professional to assess your overall situation before making any changes to diet or physical activity.
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