BMI calculator
Body mass index with the WHO classification
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What is BMI calculator?
Body mass index (BMI) relates your weight to your height and serves as a quick reference to know whether your weight is within a healthy range. Enter your weight and height and you'll see your BMI on a color scale.
It also shows the weight range considered normal for your height and how many kilos you are from it. It's a rough guide, not a diagnosis.
How to use it
- Choose the system: kg and cm or lb and ft.
- Enter your weight.
- Enter your height (in feet and inches if you use imperial units).
- Check your BMI, your WHO category and the healthy weight for your height.
Advantages
- Full WHO classification, from severe thinness to class III obesity.
- Healthy weight range for your height.
- Supports metric and imperial units.
- Free, no sign-up and no ads.
Technical details
BMI is calculated as weight (kg) / height (m)². In imperial units, pounds are converted with 1 lb = 0.45359237 kg and height with 1 in = 2.54 cm (1 ft = 12 in). The classification is the WHO one for adults: severe thinness < 16; moderate 16–16.99; mild 17–18.49; normal weight 18.5–24.99; overweight 25–29.99; class I obesity 30–34.99, class II 35–39.99 and class III ≥ 40. Healthy weight is calculated as 18.5 × height² and 24.9 × height². Only heights from 50 to 260 cm and weights from 2 to 500 kg are accepted. BMI doesn't distinguish muscle from fat and doesn't apply to people under 18 or during pregnancy.
Frequently asked questions
How is BMI calculated?
Divide your weight in kilos by your height in meters squared. With 70 kg and 1.75 m: 70 / (1.75 × 1.75) = 22.9.
What is a normal BMI?
According to the WHO, a BMI between 18.5 and 24.9 is considered normal weight in adults. From 25 to 29.9 is overweight and 30 or above is obesity.
What is my ideal weight for my height?
The tool shows the weight range with a BMI between 18.5 and 24.9 for your height. For 1.75 m it goes from about 56.7 to 76.3 kg.
Is BMI valid for athletes or children?
It's not reliable for very muscular people, because it doesn't distinguish muscle from fat, and it's not used for people under 18 or pregnant women. Consult a healthcare professional.
Can I calculate BMI in pounds and feet?
Yes. Choose “lb and ft” and enter your weight in pounds and your height in feet and inches.
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