Check your Body Mass Index (BMI) in seconds. Enter your height and weight to see your BMI and which weight category you fall into.
1. Enter your weight in kilograms. 2. Enter your height in centimetres. 3. Click Calculate BMI.
BMI stands for Body Mass Index. It is a simple number that shows whether your weight is healthy for your height. Doctors, gyms and health apps all over the world use BMI as a first check, because it needs only two numbers: your weight in kilograms and your height in centimetres. Enter those two numbers in this free BMI calculator and it shows your BMI and your weight category in seconds: underweight, healthy weight, overweight or obese.
BMI is popular because it is quick, free and easy to understand. You do not need a doctor, a scale that measures body fat, or any special equipment. It is a useful starting point for anyone who wants to lose weight, gain weight, or simply check that their weight is in a healthy range. Millions of people check their BMI every year before starting a diet or a fitness plan, and this calculator gives the same result a doctor would get from the same formula.
Take a person who weighs 70 kg and is 175 cm tall. First convert the height to metres: 1.75 m. Then square it: 1.75 times 1.75 is 3.0625. Then divide the weight by that number: 70 divided by 3.0625 is 22.9. So the BMI is 22.9, which is in the healthy range. Another example: a person who weighs 90 kg and is 170 cm tall has a BMI of 31.1, which is in the obese range, while a person who weighs 55 kg and is 170 cm tall has a BMI of 19.0, which is healthy.
The BMI formula is: BMI = weight in kilograms divided by (height in metres times height in metres). The standard adult categories are: below 18.5 is underweight, 18.5 to 24.9 is healthy weight, 25 to 29.9 is overweight, and 30 or above is obese. These ranges come from the World Health Organization and are used by health services in most countries. The ranges are the same for adult men and women, but they are not used for children, whose BMI is judged against age-based growth charts.
Weigh yourself in the morning. Your weight changes during the day, so weighing yourself at the same time each day gives the most honest result. Measure your height correctly. Stand straight against a wall without shoes and ask someone to mark the top of your head. Use BMI as a guide, not a diagnosis. A high BMI can be a warning sign, but only a doctor can judge your real health. Check again after a few months. Healthy weight change is slow, so recheck your BMI every two or three months. Pair BMI with other checks. Waist size, blood pressure and how active you feel also matter, so look at the full picture, not one number.
Muscle, age and body shape matter too. Two people with the same BMI can look very different: one may carry more muscle and the other more body fat, because muscle is denser than fat. Age matters as well, because older adults naturally carry a little more fat at the same BMI. That is why doctors use BMI together with waist size, blood pressure and blood tests, instead of judging health from one number alone.
Take a person who weighs 85 kg and is 180 cm tall. Convert the height to metres (1.80 m), square it (3.24), and divide 85 by 3.24, which gives a BMI of 26.2, in the overweight range. Now take a person who weighs 60 kg and is 165 cm tall: 60 divided by (1.65 times 1.65, which is 2.7225) gives a BMI of 22.0, in the healthy range. The same formula works for everyone: weight in kilograms divided by height in metres squared. Try both examples in the calculator above and check that your results match.
Entering height in the wrong unit. The calculator needs centimetres: 175, not 1.75 and not 5 feet 9 inches. Weighing yourself after a big meal. Food and water can add a kilogram or more, so weigh yourself at the same time each day. Measuring height with shoes on. Shoes add 2 to 3 centimetres and make your BMI look lower than it really is. Treating BMI as a full health test. BMI does not measure body fat, muscle or fitness, so use it as a starting point, not a diagnosis. Checking once and worrying. Weight changes day to day, so check again after a few weeks before you draw any conclusion.
Pro Tip: Write down your BMI and the date, then recheck every month. Slow, steady change over months is the healthiest kind of progress.
Note: This calculator shows adult BMI categories only. Children's BMI must be judged against age-based growth charts, and a doctor should interpret the result.
What is a healthy BMI? For most adults, a BMI between 18.5 and 24.9 is considered healthy. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese.
Is BMI accurate for everyone? BMI is a useful screening guide, but it is not perfect. It does not measure body fat directly, so athletes with a lot of muscle can have a high BMI while being very fit. It is also less accurate for older people, pregnant women and children.
How is BMI calculated? BMI = weight in kilograms divided by height in metres squared. For example, 70 kg divided by (1.75 times 1.75) equals a BMI of 22.9.
What should I do if my BMI is too high? Do not panic. Small, steady changes work best: eat a little less, move a little more, and recheck your BMI after a few months. For personal advice, talk to a doctor or a dietitian.
Can children use this BMI calculator? The formula is the same, but the result must be judged against age and sex growth charts, not adult ranges. This calculator shows adult categories only.
Does this calculator save my weight or height? No. The calculation happens in your browser only. Your weight and height are never sent to our servers or stored anywhere.
Can I calculate BMI in pounds and inches? This calculator uses kilograms and centimetres. To convert, divide pounds by 2.2 to get kilograms, and multiply feet by 30.48 to get centimetres.
How often should I check my BMI? Once a month is enough. Healthy weight change is slow, so daily checks mostly show water and food changes, not real progress.