BMI calculator
Body mass index (BMI) compares your weight with your height. Enter your height in centimeters or feet and inches and your weight in kilograms, pounds or stone. You will see your BMI, where it falls on the Asian or international (WHO) scale, and a clear explanation of what the number can and cannot tell you. BMI is a screening measure, not a diagnosis.
Your measurements
For adults aged 18 and over. The Asian standard is recommended for people of South Asian, East Asian and Southeast Asian origin, who face higher health risk at a lower BMI. Measure your waist at the level of your belly button for the waist-to-height ratio.
Your BMI
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Healthy weight for your height
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To reach the healthy range
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Waist-to-height ratio
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Show the working
BMI is weight in kilograms divided by height in meters squared:
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This is a screening tool, not a medical diagnosis. BMI cannot tell you whether you are healthy. It does not measure body fat, muscle, bone density or where fat is stored and it does not account for age, sex, ethnicity or medical history. Talk to a doctor or a registered dietitian before making decisions about your weight, and treat any single number here as one small input among many.
How to use this calculator
- Choose your standard. The international (WHO) standard counts a BMI of 25 or more as overweight and 30 or more as obese. The Asian standard uses 23 and 27.5, because the same BMI carries more health risk for people of Asian origin.
- Choose your units. Use the dropdown beside each box. Height can be in centimeters, feet and inches, meters or inches, and weight in kilograms, pounds or stone. You can mix units, and your choice is saved in the shared link.
- Enter your height. Measure without shoes, standing straight against a wall. An error of two centimeters changes an adult's BMI by about half a point.
- Enter your weight. If you can, weigh yourself in the morning before eating, because normal daily changes of one to two kilograms will move the result.
- Add your waist if you can. This is optional. It gives your waist-to-height ratio, which picks up fat around the middle that BMI misses.
What your BMI means
The standard adult categories are: under 18.5 is underweight, 18.5 to 24.9 is a healthy weight, 25 to 29.9 is overweight and 30 or more is obese. These cut-offs come from population studies; they are not sharp biological boundaries, and nothing important changes between a BMI of 24.9 and 25.1.
They are also not used everywhere. Health bodies in several countries use lower cut-offs for people of South Asian, Chinese and some Southeast Asian backgrounds, because their risk of diabetes and heart disease starts to rise at a lower BMI. If that applies to you, a BMI just under 25 may not be as healthy as it looks.
BMI ranges for Asian adults
The usual ranges, with overweight from 25 and obese from 30, were based mainly on data from European populations. Studies across Asia found that people of South Asian, East Asian and Southeast Asian origin develop type 2 diabetes and heart disease at a lower BMI. At the same weight, they tend to carry more body fat, and more of it around the middle.
A World Health Organization expert group therefore set lower cut-offs for Asian populations: overweight from 23 and obese from 27.5. For most adults in Pakistan, India and Bangladesh, the Asian standard is the better guide. The calculator chooses it automatically for visitors in Asia, and it also tells you how the other standard would classify the same BMI, so you can see the difference.
Waist-to-height ratio
If you add your waist measurement, the calculator divides it by your height. The rule of thumb is simple: keep your waist to less than half your height, which means a ratio under 0.5. A ratio between 0.5 and 0.6 suggests extra fat around the middle, and 0.6 or more is linked with a clearly higher health risk. This catches the situation BMI misses most often: a normal BMI with a large waist.
Your target weight
If your BMI is outside the healthy range, the result shows the weight at the nearest edge of that range and a rough timeline to reach it. The timeline assumes you lose 0.5 kg a week or gain 0.25 kg a week, which are the steady rates health services generally recommend. The calculator never suggests a target weight below the healthy range.
Where BMI can mislead
Apart from height, BMI only uses your total weight. It cannot tell what that weight is made of, which leads to two common mistakes.
It can count muscle as excess weight. An athlete with a lot of muscle often falls in the overweight or even obese range while having low body fat and excellent health. The number is mathematically correct but tells you little about that person.
It can miss hidden fat. The opposite case is more common and more serious. Someone with a BMI of 23 can still carry a lot of fat around their internal organs, which is the type of fat most strongly linked to heart disease and diabetes. BMI would still class them as healthy.
BMI also cannot tell where your fat is stored. Two people with the same BMI, one carrying weight around the stomach and the other around the hips, have different levels of health risk. That is why waist measurements and the waist-to-height ratio are now widely used alongside BMI.
What to do with your result
A BMI in the healthy range is a reassuring sign, but it does not prove that everything is fine. Your blood pressure, resting heart rate, cholesterol and blood sugar tell you more about your health.
If your BMI is outside the healthy range, treat it as a reason to look more closely, not as a final judgment. Measure your waist, and think about any recent changes in your sleep, activity or stress levels. If the number worries you, talk to a doctor, who can look at it together with everything BMI cannot measure.
Frequently asked questions
What is a healthy BMI?
For adults, a healthy BMI is usually 18.5 to 24.9, or 18.5 to 22.9 under the Asian standard. These ranges come from population studies and show where health risk is lowest on average, not the exact weight any one person should be.
What is a healthy BMI for Asians and Pakistanis?
For people of Asian origin, including Pakistanis, the World Health Organization suggests a healthy range of 18.5 to 22.9, with overweight starting at 23 and obesity at 27.5. The lower cut-offs reflect a higher risk of diabetes and heart disease at the same BMI.
How do I calculate BMI with feet and inches?
Choose “ft + in” as the height unit and enter your height, for example 5 feet 7 inches. The calculator converts it for you. To do it by hand, convert your height to meters (1 inch is 0.0254 m), then divide your weight in kilograms by your height in meters squared.
What is a good waist-to-height ratio?
Under 0.5, which means your waist measures less than half your height. A ratio between 0.5 and 0.6 suggests extra fat around the middle, and 0.6 or more is linked with a clearly higher health risk.
Is BMI accurate for everyone?
No. It works reasonably well across large groups of people but can be misleading for individuals, especially athletes, older adults who have lost muscle, pregnant women and anyone whose build differs from the average.
Can I use this BMI calculator for children?
No. Children and teenagers are assessed with growth charts based on their age and sex, because a healthy body shape changes as they grow. Use a pediatric BMI chart or ask your child's doctor.
Is body fat percentage better than BMI?
Body fat percentage tells you more, because it separates fat from muscle, but it is harder to measure accurately. Home body fat scales are unreliable, and accurate methods such as a DEXA scan need a clinic. Our body fat calculator uses the US Navy tape method, which is a reasonable middle ground.
Why does my BMI differ between calculators?
Usually because of rounding, or because the units are converted at a different step. Differences under 0.2 do not matter. Bigger differences usually mean the other calculator uses a different formula, such as the newer Trefethen BMI.