Free BMI Calculator
Calculate your Body Mass Index in seconds and understand what your result may mean.
- Metric & imperial units
- No sign-up needed
- Runs in your browser
Calculate Your Body Mass Index
Choose your units, enter your details, and get your BMI instantly. Nothing you type leaves your device.
Your BMI result
Your BMI
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BMI is a screening measure. It does not directly measure body fat or diagnose any health condition.
BMI is a screening measure only. It does not directly measure body fat or diagnose health conditions, and adult categories are not used for people under 20.
What Is Body Mass Index (BMI)?
A quick measure of weight for height
Body Mass Index, or BMI, is a single number that compares your weight with your height. Because it only needs two simple measurements, it has become one of the most widely used ways to get a general picture of whether a person’s weight sits within a typical range for their height.
How it is used
Doctors, researchers, and public health organizations use BMI as a starting point. It can help spot weight changes over time and highlight when it may be worth looking more closely at someone’s health. Across large groups of people, it is a practical way to study trends.
Its limitations
BMI is helpful, but it is not the full story. Keep these points in mind:
- It does not tell muscle apart from fat. A muscular athlete can have a high BMI with little body fat.
- It says nothing about where fat is stored, which can matter for health.
- Age, sex, ethnicity, body build, and pregnancy can all change how a result should be read.
- Adult categories do not apply to children and teenagers under 20.
The best way to use a BMI calculator is as one piece of information, read in context alongside other measures and, if you have questions, a conversation with a healthcare professional.
Standard Adult BMI Categories
These BMI categories are commonly used for adults aged 20 and older. They describe weight ranges, not health on their own.
Underweight
Below 18.5Weight is lower than the range usually used as a reference for this height.
Healthy weight
18.5 to below 25Weight falls within the range commonly considered healthy for this height.
Overweight
25 to below 30Weight is above the healthy-weight reference range for this height.
Obesity
30 and aboveWeight is in the highest standard range for this height.
Every body is different. A BMI category is a screening result, and a healthcare professional can help put it in context with your overall health.
How to Use the BMI Calculator
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Enter your height
Choose metric or imperial units, add your age, then type your height in centimeters or in feet and inches.
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Enter your weight
Add your weight in kilograms or pounds. Measuring without heavy clothing or shoes gives a more accurate number.
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Calculate and review
Press Calculate BMI to see your result, your category, and where it sits on the BMI scale.
Frequently Asked Questions
What is BMI?
BMI stands for Body Mass Index. It is a number calculated from your height and weight that gives a quick, general estimate of whether your weight falls within a commonly used reference range for your height. It is a screening measure, not a diagnosis.
How is BMI calculated?
BMI is your weight in kilograms divided by your height in meters squared (kg/m²). If you use pounds and inches, the formula is 703 × weight (lb) ÷ height (in)². Both methods give the same result.
What is a healthy adult BMI range?
For adults aged 20 and older, a BMI from 18.5 to below 25 is generally classed as the healthy weight range. Below 18.5 is classed as underweight, 25 to below 30 as overweight, and 30 or above as obesity.
Is BMI accurate for everyone?
No. BMI is useful for looking at trends across large groups of people, but it can be less informative for individuals. Factors such as muscle mass, age, sex, ethnicity, body shape, and pregnancy can affect how a BMI result should be interpreted. A healthcare professional can look at BMI alongside other information.
Can BMI distinguish muscle from fat?
No. BMI uses only total body weight and height, so it cannot tell how much of that weight comes from muscle, fat, bone, or water. A very muscular person may have a high BMI without having excess body fat.
Can children use the adult BMI calculator?
The adult BMI categories should not be used for children and teenagers under 20. Their BMI is interpreted using age- and sex-specific growth charts, which compare a child’s BMI with others of the same age and sex. A pediatrician or healthcare provider can help interpret a child’s BMI.
Educational Use Only
This BMI calculator is provided for general educational and informational purposes. It is not a substitute for professional medical advice, diagnosis, or treatment.
Your result is calculated using the standard BMI formula and the adult BMI categories described on this page. If you have questions about your weight or health, please speak with a qualified healthcare professional.