BMI Calculator
Calculate your Body Mass Index from your height and weight and get a quick general BMI category estimate.
Calculate Your BMI
Choose your preferred units, enter your height and weight, and calculate your BMI instantly.
What Is BMI?
Body Mass Index, commonly called BMI, is a numerical measure calculated from a person's weight and height. It is commonly used as a screening measure to place adult weight relative to height into broad categories.
BMI is useful as a simple calculation, but it is not a complete assessment of an individual's health or body composition. Factors such as muscle mass, age, sex, fitness, medical history, and other characteristics can affect how BMI should be interpreted.
How to Use the BMI Calculator
- Choose Metric or Imperial units.
- Enter your height.
- Enter your weight.
- Click Calculate BMI.
- Review your BMI value and the general adult BMI category shown by the tool.
BMI Formula
In metric units, BMI is calculated by dividing weight in kilograms by height in meters squared.
For example, a person weighing 70 kg and measuring 1.75 m tall has a BMI of approximately 22.9.
When using imperial measurements, BMI can be calculated from weight in pounds and height in inches using the appropriate conversion factor. This calculator handles the conversion automatically.
Adult BMI Categories
Underweight
BMI below 18.5.
Healthy Weight
BMI from 18.5 to less than 25.
Overweight
BMI from 25 to less than 30.
Obesity
BMI of 30 or higher.
These broad categories are intended for adults. BMI categories are not interpreted in exactly the same way for children and teenagers.
Example BMI Calculation
Weight: 70 kg
Height: 175 cm = 1.75 m
Calculation:
70 ÷ (1.75 × 1.75) = 22.86
Result:
BMI ≈ 22.9
This example falls within the general adult healthy-weight BMI range. A BMI category by itself should not be treated as a diagnosis or a complete description of an individual's health.
Why Use a BMI Calculator?
Calculating BMI manually requires converting measurements and applying the formula. A calculator provides a faster way to perform the arithmetic and reduces the chance of calculation errors.
Quick Screening Calculation
BMI can provide a quick numerical screening measure based on height and weight.
Metric and Imperial Units
The tool supports both metric and imperial measurements, so you can use kilograms and centimeters or pounds with feet and inches.
Easy Comparison
The BMI value can make it easier to understand where a person's height and weight combination falls within broad adult BMI categories.
Important Limitations of BMI
BMI does not distinguish between muscle, bone, fat, and other components of body weight. A person with substantial muscle mass may have a higher BMI without having excess body fat. BMI also does not provide a complete picture of an individual's health.
For these reasons, BMI results should be considered alongside other relevant information rather than used on their own to make health decisions.
Who Should Be Careful When Interpreting BMI?
Standard adult BMI categories may not be appropriate for every person. Children and teenagers require age- and sex-specific interpretation. Pregnant people should also not use standard BMI categories to assess pregnancy weight status.
Athletes and people with unusually high muscle mass may also find that BMI does not accurately represent body-fat levels. If you are concerned about your weight or health, a qualified healthcare professional can provide a more complete assessment.
Common BMI Calculation Mistakes
- Entering height in centimeters when the metric formula requires meters.
- Confusing pounds with kilograms.
- Entering inches as feet or feet as inches.
- Rounding height too aggressively before calculating BMI.
- Treating a BMI category as a medical diagnosis.
Frequently Asked Questions
What is BMI?
BMI, or Body Mass Index, is a numerical measure calculated from weight and height and commonly used as a screening measure for adults.
How is BMI calculated?
In metric units, BMI is calculated by dividing weight in kilograms by height in meters squared.
What is a normal BMI?
For adults, a BMI from 18.5 to less than 25 is commonly classified as the healthy-weight category.
Is BMI the same as body fat percentage?
No. BMI uses only height and weight. It does not directly measure body fat percentage or body composition.
Can children use this BMI calculator?
Standard adult BMI categories should not be used to interpret BMI in children and teenagers. Their BMI is interpreted using age- and sex-specific growth references.
Can athletes have a high BMI?
Yes. People with higher muscle mass may have a higher BMI because BMI does not distinguish muscle from fat.
Can BMI diagnose a health condition?
No. BMI is a screening measure and should not be treated as a diagnosis or a complete assessment of health.
Related Tools
Calculate Your BMI
Enter your height and weight above to calculate your BMI and view the corresponding general adult BMI category.
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