BMI calculator
Enter your weight and height to see your body mass index, its category and the weights that give a healthy index at your height. There is one tool in pounds, feet and inches and one in kilograms and centimeters.
In pounds, feet and inches
This answer is for the example values in the boxes above. 165 pounds, 69 inches tall. Change the boxes to see your own answer.
The body mass index estimates body fat from height and weight. It does not take into account muscle mass, bone density or body composition, and a health care provider will consider whether a figure is too high or too low for you.
The categories are those for adults of 20 and older. Do not use them for a child: the child's provider can say what weight is right for the child's age.
In kilograms and centimeters
The body mass index estimates body fat from height and weight. It does not take into account muscle mass, bone density or body composition, and a health care provider will consider whether a figure is too high or too low for you.
The categories are those for adults of 20 and older. Do not use them for a child: the child's provider can say what weight is right for the child's age.
How it works
The body mass index compares weight with height. In kilograms and meters it is the weight divided by the height squared, which is how the World Health Organization writes it. In pounds and inches the calculator follows the hand method of MedlinePlus: the weight times 703, divided by the height in inches twice.
The index is shown to one decimal, and the category is read from that figure. For adults of 20 and older the National Institutes of Health name four ranges, and the calculator also gives the weights that fall in the healthy one at your height.
A worked example
MedlinePlus works the example of a woman who weighs 270 pounds and is 68 inches tall: her BMI is 41.0. The calculator gives the same figure, which is in class 3 of obesity.
A person of 165 pounds and 5 feet 9 inches has a BMI of 24.4, a healthy weight. At that height the healthy range is 125.3 to 168.6 pounds. In kilograms, 75 kilograms at 178 centimeters gives 23.7, and the healthy range at that height is 58.6 to 78.9 kilograms.
The categories
Below 18.5 is underweight. From 18.5 to 24.9 is a healthy weight, from 25.0 to 29.9 overweight, and 30.0 or more obesity. MedlinePlus splits obesity into three classes: class 1 from 30 to under 35, class 2 from 35 to under 40, and class 3, which it calls severe obesity, at 40 or more.
What it leaves out
The index is a measure of body fat from height and weight. It does not take into account muscle mass, bone density or body composition, and MedlinePlus says that people who are very muscular may have a high BMI. The NHLBI says that your provider will consider whether your BMI is too high or too low for you.
The categories are for adults. Do not use them for a child: MedlinePlus says not to use its BMI calculator for evaluating a child and to ask the child’s provider, and the World Health Organization says that age needs to be considered for children. MedlinePlus also says that for people of 65 or older a slightly higher BMI may help protect against thinning of the bones, and that it is best to talk to a provider before trying to lose or gain weight.
Sources
- National Heart, Lung, and Blood Institute, Calculate Your Body Mass Index, read on 2026-11-02.
- MedlinePlus, Body mass index (BMI), of the National Library of Medicine, read on 2026-11-02.
- National Institute of Diabetes and Digestive and Kidney Diseases, Definition & Facts for Adult Overweight & Obesity, read on 2026-11-02.
- World Health Organization, Obesity and overweight (fact sheet), read on 2026-11-02.
Questions
How do you calculate BMI?
With pounds and inches, multiply the weight by 703, divide by the height in inches, and divide by the height in inches again. With kilograms and meters, divide the weight by the height squared. A weight of 165 pounds at 5 feet 9 inches gives 24.4.
What is a healthy BMI?
For adults the National Institutes of Health call a BMI of 18.5 to 24.9 a healthy weight, 25.0 to 29.9 overweight and 30.0 or more obesity. A BMI under 18.5 is underweight. Obesity has three classes: 30 to under 35, 35 to under 40, and 40 or more.
Is BMI accurate for everyone?
No. It is based on height and weight and does not take into account muscle mass, bone density or body composition, the NHLBI says. MedlinePlus adds that a very muscular person may have a high BMI and that healthy ranges for older adults differ.
Can I use a BMI calculator for a child?
No. MedlinePlus says not to use its BMI calculator to evaluate a child, and the World Health Organization says that age needs to be considered when defining overweight and obesity in children. The child’s provider can say what weight is right for the child’s age.
How much should I weigh for my height?
The weights that give a BMI of 18.5 to 24.9 are the healthy range. At 5 feet 9 inches it is 125.3 to 168.6 pounds, and at 178 centimeters it is 58.6 to 78.9 kilograms. A health care provider decides what is right for you.
Published . Updated .