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A BMI calculator is a simple way to estimate your Body Mass Index using your height and weight. BMI can help you understand whether your weight falls within a commonly used range for your height and can provide a useful starting point for thinking about your overall health.
Enter your height and weight into the calculator to calculate your BMI. The result can then be compared with standard adult BMI ranges, including underweight, healthy weight, overweight, and obesity.
BMI is useful as a screening measure, but it is not a complete measure of health. Factors such as muscle mass, body composition, medical history, activity level, and other health measurements can also matter.
BMI stands for Body Mass Index. It is a calculated value based on a person’s weight and height.
For adults, BMI is calculated by dividing weight in kilograms by height in meters squared. The result is expressed in kilograms per square meter (kg/m²).
BMI is commonly used as a quick screening tool because it provides a simple way to compare weight with height. It can help identify whether an adult’s weight falls into an underweight, healthy weight, overweight, or obesity category.
However, BMI does not directly measure body fat. Two people can have the same BMI while having different amounts of muscle and body fat.
A BMI calculator uses two main measurements: height and weight.
After you enter these measurements, the calculator applies the BMI formula and provides a numerical result.
For metric measurements: BMI = Weight (kg) ÷ Height² (m²).
For people using pounds and inches: BMI = 703 × Weight (lb) ÷ Height² (in²). The calculator can then compare the result with standard adult BMI categories.
Calculating BMI manually is straightforward when you know your height and weight.
Measure your current body weight. You can use kilograms or pounds depending on the calculator.
Measure your height accurately. You can enter it in centimeters, meters, feet, or inches depending on the available calculator options.
For metric measurements: BMI = weight in kilograms ÷ height in meters².
For example, if someone weighs 70 kg and is 1.75 meters tall: BMI = 70 ÷ (1.75 × 1.75) ≈ 22.9. The resulting BMI can then be compared with the standard adult BMI categories.
The standard BMI formula for adults is: BMI = kg / m².
Where kg = body weight in kilograms, m = height in meters, and m² = height multiplied by itself.
For pounds and inches: BMI = (weight in pounds × 703) ÷ height in inches². An online BMI calculator automatically performs these calculations, reducing the possibility of arithmetic errors.
The following table shows the commonly used BMI categories for adults aged 20 and older:
BMI Range | Category |
Below 18.5 | Underweight |
18.5 to 24.9 | Healthy Weight |
25.0 to 29.9 | Overweight |
30.0 or higher | Obesity |
30.0 to 34.9 | Class 1 Obesity |
35.0 to 39.9 | Class 2 Obesity |
40.0 or higher | Class 3 Obesity |
These categories are used for adults regardless of sex. BMI should be considered alongside other health information rather than used as a diagnosis by itself.
For adults, a BMI from 18.5 to less than 25 is generally classified as the healthy-weight range.
This range can be useful as a general reference, but having a BMI in this range does not automatically mean that a person is healthy in every respect.
Similarly, a BMI outside this range does not provide enough information by itself to determine an individual’s overall health. A healthcare provider may consider other factors such as blood pressure, blood glucose, cholesterol, physical activity, diet, medical history, and body composition.
A BMI calculator for men uses the same basic adult BMI formula as a calculator for women. For adults, the standard BMI categories do not change based on whether the person is male or female.
However, BMI does not account for differences in muscle mass or body composition.
A muscular person may have a higher BMI because muscle contributes to body weight even when their body-fat level is relatively low.
Therefore, BMI can be a useful screening measurement for men, but it should not be interpreted as a direct measurement of body fat.
For a more complete approach to overall health and daily wellness, you can also use a Sleep Calculator to understand your ideal sleep schedule and support healthier habits.
A BMI calculator for women also uses height and weight to calculate BMI. For adult women, the standard adult BMI categories are the same: below 18.5 underweight, 18.5–24.9 healthy weight, 25–29.9 overweight, and 30 or higher obesity.
BMI does not directly measure body fat, and it does not account for every factor that can affect a woman’s health or body composition. For pregnancy, BMI should not be used in the same way as a general adult weight assessment. Pregnancy-related weight guidance is different and should be discussed with an appropriate healthcare professional.
If you want to know what your BMI is, use the BMI calculator and enter your current height and weight.
For the most useful result: measure your height accurately, use a reliable weight measurement, select the correct measurement units, enter the information into the calculator, and review the BMI number and category.
Your BMI is only one piece of information. It should be interpreted in the context of your overall health.
There is no single weight that is ideal for every person. The amount you weigh can vary depending on your height, body composition, muscle mass, age, and other factors.
Instead of asking only How much should I weigh?, it can be more useful to consider whether your weight falls within a generally healthy range for your height and whether other health indicators are favorable. BMI can provide a starting point for this assessment.
For adults, the healthy BMI range is 18.5 to less than 25. You can use that range with your height to estimate the corresponding weight range.
People often search for terms such as ideal body weight, ideal weight for height, or what weight should I be. However, there is not one universally correct body weight for everyone.
BMI can provide a standardized reference based on height and weight, but it should not be treated as a perfect ideal-weight calculator. A healthy weight goal should also take into account your individual circumstances, body composition, lifestyle, and health history.
Your BMI changes when either your height or weight changes. For example, a person weighing 70 kg will have a different BMI depending on whether they are 1.60 m, 1.70 m, or 1.80 m tall.
Weight | Height | Approximate BMI |
60 kg | 1.60 m | 23.4 |
70 kg | 1.70 m | 24.2 |
70 kg | 1.75 m | 22.9 |
80 kg | 1.80 m | 24.7 |
90 kg | 1.80 m | 27.8 |
These examples demonstrate how the same or similar weight can produce different BMI results depending on height.
A BMI of 20 falls within the healthy-weight range for an adult.
A BMI of 24 is also within the healthy-weight range for an adult.
A BMI of 27 falls within the overweight category for an adult.
A BMI of 32 falls within the Class 1 obesity category for an adult. Remember that these categories are screening categories and should not be interpreted as a diagnosis.
For adults, a BMI from 18.5 to less than 25 is commonly categorized as healthy weight. People sometimes use the term “normal BMI” to describe this range.
It is important to remember that BMI categories are population-level screening ranges. Your personal health cannot be determined from BMI alone.
BMI can be useful, but it has limitations. One of its biggest limitations is that BMI does not distinguish between muscle, fat, bone, and other components of body weight.
For example, an athlete with substantial muscle mass may have a relatively high BMI without having the same body-fat level as another person with the same BMI. BMI also does not show where fat is stored in the body.
For these reasons, BMI should be viewed as a screening tool rather than a complete assessment of body composition or health.
BMI and body-fat percentage are different measurements. BMI uses height and weight. Body-fat percentage estimates how much of your total body weight is fat.
A person can have the same BMI as another person but have a different body-fat percentage because their muscle and fat proportions are different.
If you need a more detailed assessment of body composition, methods such as skinfold measurements, bioelectrical impedance, DEXA scans, or other professional assessments may be used. However, each method has its own limitations and accuracy considerations.
Adult BMI categories should not be applied directly to children and teenagers. For children and teens ages 2 through 19, BMI is interpreted according to age- and sex-specific BMI-for-age percentiles because children are still growing.
BMI-for-Age Percentile | Category |
Below 5th percentile | Underweight |
5th to below 85th percentile | Healthy Weight |
85th to below 95th percentile | Overweight |
95th percentile or higher | Obesity |
A child or teenager’s BMI should therefore be evaluated using an appropriate child and teen BMI calculator rather than an adult BMI chart.
For adults, standard BMI categories are generally applied to adults 20 and older without separate BMI cutoffs based on age.
For children and teenagers, age is important because BMI is interpreted using age- and sex-specific percentiles. This distinction is important when choosing a BMI calculator.
For adults, the standard BMI category ranges are the same for men and women. However, BMI does not capture differences in body composition between individuals. This is one reason why BMI should not be used as the only measure of health.
For children and teenagers, BMI interpretation does use age- and sex-specific percentiles.
A BMI of 18 is below the standard adult healthy-weight range and falls into the underweight category. However, one BMI result does not explain why someone has a particular weight. Factors such as nutrition, medical conditions, activity level, and individual circumstances may need to be considered.
A BMI of 20 falls within the healthy-weight range for adults. BMI should still be considered as one health indicator rather than a complete health assessment.
A BMI of 25 is at the beginning of the adult overweight category under commonly used BMI classifications. Because BMI is a screening measure, a result around a category boundary should not be interpreted in isolation.
A BMI of 30 falls within the obesity category for adults and is the beginning of Class 1 obesity under the standard adult classification. If you are concerned about your BMI or weight, discussing the result with a healthcare professional can help put it into context.
A BMI of 40 or higher falls into Class 3 obesity, also called severe obesity, in standard adult BMI classifications. A higher BMI can be associated with increased health risks, but BMI alone cannot determine an individual’s health status or medical diagnosis.
If your BMI is outside the healthy-weight range and you want to change it, focus on sustainable health habits rather than extreme short-term changes.
Helpful habits may include eating a balanced diet, choosing nutrient-dense foods, getting regular physical activity, getting adequate sleep, managing stress, limiting excessive intake of highly processed foods, and maintaining consistent healthy routines.
The appropriate approach depends on the individual. Rapid or extreme weight-loss methods are not appropriate for everyone. If you have a medical condition, are pregnant, take medications that affect weight, or have concerns about your weight, speak with a qualified healthcare professional before making major changes.
A BMI calculator cannot tell you your exact body-fat percentage, where your body stores fat, your cardiovascular fitness, blood pressure, blood sugar, cholesterol, muscle mass, complete nutritional status, or whether you have a specific disease.
This is why BMI is best used as a starting point rather than a final health judgment.
An online BMI calculator can make BMI calculation quick and convenient. Instead of manually converting units and applying the formula, you can enter your height and weight and receive a BMI result immediately.
A useful calculator should be simple to use, support common measurement units, clearly display the BMI result, explain the BMI category, provide a readable BMI chart, work well on mobile devices, avoid unnecessary steps, and explain the limitations of BMI.
The calculator should also make it clear whether it is intended for adults, children, or both.
body mass calculator
Use weight in kilograms and height in meters. Formula: BMI = kg ÷ m².
Use weight in pounds and height in inches. Formula: BMI = 703 × lb ÷ in².
An online BMI calculator can handle the conversion and calculation automatically.
Adult BMI charts for men and women generally use the same BMI category thresholds.
BMI | Adult Category |
Under 18.5 | Underweight |
18.5–24.9 | Healthy Weight |
25–29.9 | Overweight |
30–34.9 | Class 1 Obesity |
35–39.9 | Class 2 Obesity |
40+ | Class 3 Obesity |
The chart provides a quick reference, while the calculator provides an individualized BMI result based on height and weight.
BMI has remained popular because it is simple, inexpensive, and easy to calculate. However, simplicity is also its limitation.
BMI does not directly measure body fat and can sometimes classify muscular individuals differently from what a body-composition assessment would suggest. It also does not account for every health factor.
Therefore, a BMI result should be interpreted together with other relevant information.
Consider speaking with a healthcare professional if you are concerned about your weight, your weight has changed significantly without an obvious reason, you are having difficulty gaining or losing weight, you have symptoms or medical concerns, you are pregnant, you are calculating BMI for a child or teenager, you want personalized weight-management guidance, or you have concerns about eating or body image.
A healthcare professional can consider information that a BMI calculator cannot.
A BMI calculator is a convenient way to calculate Body Mass Index and understand how your weight compares with standard height-based categories. For adults, BMI can help identify whether a result falls within the underweight, healthy-weight, overweight, or obesity range.
However, BMI is only one part of a broader health assessment. It does not directly measure body fat, muscle mass, fitness, or overall health. Use your BMI result as a useful starting point rather than a diagnosis.
For children and teenagers, use age- and sex-specific BMI-for-age percentiles instead of adult BMI categories. If you have concerns about your weight or health, a healthcare professional can help interpret your result in the context of your individual circumstances.
BMI stands for Body Mass Index. It is a calculated measure of weight relative to height.
For adults, a BMI from 18.5 to less than 25 is classified as healthy weight.
For adults using metric measurements, divide your weight in kilograms by your height in meters squared: BMI = kg ÷ m². You can also use an online BMI calculator to perform the calculation automatically.
BMI is determined from two measurements: height and weight. The measurements are entered into the BMI formula to calculate a BMI value.
Enter your current height and weight into a BMI calculator. The calculator will calculate your BMI and show the corresponding adult category.
Your BMI depends on your height and weight. Enter both measurements into the calculator to calculate your personal BMI.
For adults, the commonly used healthy BMI range is 18.5 to less than 25.
For adults, a BMI from 25 to less than 30 falls into the overweight category.
For adults, a BMI of 30 or higher falls into the obesity category.
BMI is useful as a screening measurement, but it does not directly measure body fat and cannot provide a complete assessment of health.
The standard adult BMI category ranges are the same for men and women. However, BMI does not account for individual differences in body composition.
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