BMI Calculator (Body Mass Index)
Enter your weight and height, in pounds and feet or in kg and cm: your BMI, your WHO category and the healthy weight range for your height appear instantly. Nothing is sent anywhere.
- WHO categories
- lb/ft or kg/cm
- Healthy weight range
- Free
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How to calculate your BMI?
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Choose your units
Pounds, feet and inches, or kilograms and centimeters if you're used to metric units.
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Enter weight and height
Your BMI is calculated instantly and shown to one decimal place.
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Read your result
The color gauge places your BMI among the WHO categories, and the healthy weight range for your height is shown below.
Your BMI and what it means
BMI to one decimal place
The standard calculation, weight (kg) / height (m)², shown to one decimal place as in the WHO tables.
WHO category gauge
From underweight to class III obesity, see where you stand at a glance on a color-coded gauge.
Healthy weight for your height
The minimum and maximum weight matching a BMI between 18.5 and 24.9 for the height you entered.
Imperial or metric units
Enter pounds, feet and inches, or kg and cm: the conversion is done for you.
How is BMI calculated?
Body mass index is weight in kilograms divided by height in meters squared: BMI = weight / height². In imperial units, the formula becomes BMI = 703 × weight in pounds / (height in inches)². For someone who weighs 154 lb and is 5 ft 9 in tall, that's 69 inches: 703 × 154 / (69 × 69) = 22.7. In metric, a person of 70 kg who is 1.75 m tall has 1.75 × 1.75 = 3.0625, then 70 / 3.0625 = 22.9. Remember to convert centimeters to meters (175 cm = 1.75 m): dividing by 175 instead of 1.75 gives an absurd result. The formula and the WHO thresholds are the same for adult men and women.
BMI categories according to the WHO
For adults, the World Health Organization classifies BMI as follows: under 18.5, underweight; 18.5 to 24.9, normal (healthy) weight; 25 to 29.9, overweight; 30 to 34.9, obesity class I; 35 to 39.9, obesity class II; 40 and above, obesity class III, sometimes called severe obesity. To find the healthy weight for your height, multiply your height squared by 18.5 and then by 24.9: at 5 ft 9 in, that's roughly 125 to 169 lb, and at 1.75 m, about 57 to 76 kg. A person who is 1.60 m tall and weighs 70 kg has a BMI of 27.3, in the overweight range; they would reach a normal weight below about 64 kg.
The limits of BMI
BMI is a simple statistical indicator, not a diagnosis. It doesn't tell muscle from fat: a very muscular athlete can be classed as overweight while being perfectly healthy. Nor does it say anything about where fat is stored, even though belly fat, better reflected by waist circumference, is more closely linked to heart disease risk. The WHO thresholds only apply to adults aged 18 and over: for children and teens, doctors use BMI-for-age growth charts based on age and sex. They don't apply during pregnancy either. This calculator is not a substitute for medical advice: to interpret your result, talk to your doctor.
Frequently Asked Questions
How do I calculate my BMI?
Divide your weight in kilograms by your height in meters squared, or multiply your weight in pounds by 703 and divide by your height in inches squared. At 130 lb and 5 ft 5 in (65 in): 703 × 130 / (65 × 65) = 21.6.
What is a normal BMI?
For adults, the WHO considers a BMI between 18.5 and 24.9 to be normal. There's no single ideal number: any BMI in that range corresponds to a healthy weight.
What should I weigh for my height?
For a healthy weight, your weight should fall between 18.5 × height² and 24.9 × height², with height in meters. At 1.70 m (about 5 ft 7 in), that's roughly 53 to 72 kg, or 118 to 159 lb; the calculator shows the exact range for your height.
What BMI is considered overweight?
25 and above for adults. Obesity starts at 30, class II obesity at 35 and class III obesity at 40.
Does BMI work for children?
No, the adult thresholds don't apply under 18. For children and teens, BMI is read on growth charts by age and sex (BMI-for-age percentiles); ask your pediatrician or doctor for advice.