BMI Calculator
Calculate adult body mass index from height and weight, then see the matching BMI category.
BMI Calculator
Marker position shows where this BMI falls across adult category ranges.
This BMI calculator is for adult educational screening estimates only. It is not medical advice, diagnosis, or treatment. Talk with a healthcare professional about personal health questions.
How it works
Formula and steps
The formula shows how the bmi calculator turns your inputs into the result. Use it to check the calculation, then follow the example steps to see each part of the math.
Formula & steps
US BMI formula
BMI = 703 x lb / in^2
Use this when height is entered in feet and inches and weight is entered in pounds.
BMI= Body mass indexlb= Weight in poundsin= Total height in inches703= Conversion factor for US unitsMetric BMI formula
BMI = kg / m^2
Use this when height is entered in centimeters and weight is entered in kilograms.
BMI= Body mass indexkg= Weight in kilogramsm= Height in meters, after converting centimeters to meters- 1Enter height and weight in US or metric units.
- 2For metric units, convert height from centimeters to meters.
- 3Divide weight in kilograms by height in meters squared, or use 703 x pounds divided by inches squared.
- 4Compare the BMI number with adult BMI category ranges.
Worked examples
At 5 ft 9 in and 150 lb, BMI is about 22.1, which is in the healthy weight category.
At 175 cm and 70 kg, BMI is about 22.9, which is in the healthy weight category.
At 180 cm and 90 kg, BMI is about 27.8, which is in the overweight category.
Common uses
- BMI calculator
- Body mass index calculator
- Adult BMI estimate
- Height and weight screening
- Metric BMI calculator
- US BMI calculator
Common mistakes
- Using centimeters directly in the metric formula instead of converting height to meters first.
- Using only the inches field for US height instead of total height in inches.
- Treating BMI as a diagnosis instead of a screening estimate that may not reflect body composition or individual health.
BMI guide
How to understand your BMI result
This adult BMI calculator estimates body mass index from height and weight. Use the result as a quick screening number, then compare it with the BMI chart for adults to see which category it falls into.
The same adult BMI ranges are used for men and women. Children and teens need a different body mass index calculator because their BMI is interpreted with age- and sex-specific percentiles.
BMI chart for adults
| BMI range | Adult category | What it means |
|---|---|---|
| Below 18.5 | Underweight | BMI is below the adult healthy weight range. |
| 18.5 to 24.9 | Healthy weight | BMI is within the adult healthy BMI range. |
| 25.0 to 29.9 | Overweight | BMI is above the healthy weight range but below obesity categories. |
| 30.0 to 34.9 | Obesity class 1 | BMI is in the first adult obesity class. |
| 35.0 to 39.9 | Obesity class 2 | BMI is in the second adult obesity class. |
| 40.0 or higher | Obesity class 3 | BMI is in the highest adult obesity class. |
BMI formula examples
With US units, BMI is 703 times weight in pounds divided by height in inches squared. A person who is 5 ft 9 in and 150 lb has a BMI of about 22.1.
With metric units, BMI is weight in kilograms divided by height in meters squared. A person who is 175 cm and 70 kg has a BMI of about 22.9.
What BMI can and cannot tell you
BMI can help screen for adult weight categories, but it does not directly measure body fat, muscle mass, pregnancy status, age-related body composition, or where body fat is distributed.
Athletes and people with higher muscle mass can have a high BMI without the same body composition as someone with less muscle. Use BMI as one data point, not a diagnosis.
FAQ
BMI means body mass index. It is a calculation that compares body weight with height to estimate an adult weight category.
For metric units, divide weight in kilograms by height in meters squared. For US units, multiply weight in pounds by 703, then divide by height in inches squared.
Adult BMI categories are underweight below 18.5, healthy weight from 18.5 to less than 25, overweight from 25 to less than 30, and obesity at 30 or greater.
For adults, the healthy BMI range is 18.5 to less than 25. BMI is only a screening estimate, so personal health questions should be discussed with a healthcare professional.
Adult BMI uses the same formula and category ranges for men and women. Body composition can still differ, so BMI should not be treated as a complete health assessment.
Yes. Athletes and people with higher muscle mass can have a BMI in the overweight range even when BMI does not reflect the same body fat level as another person.
BMI is useful as a quick screening measure for adults, but it does not directly measure body fat, muscle mass, fat distribution, pregnancy, or individual medical risk.
BMI divides weight by height squared to scale weight relative to body size. It is a simple population screening formula, not a precise body composition measurement.
No. This calculator uses adult BMI categories. Children and teens need age- and sex-specific BMI percentiles.
No. BMI is a screening measure. A healthcare professional can interpret it with other information such as medical history, physical exam findings, and lab results.
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