BMI Calculator

Use our free BMI Calculator to calculate your Body Mass Index based on your height and weight. Enter your age, select your gender, and choose either Metric or Imperial units to calculate your BMI.

Your results include your BMI score, BMI category, estimated healthy weight range, and BMI Prime. You can use the calculator with kilograms and centimeters or pounds, feet, and inches.

What Is BMI?

Body Mass Index (BMI) is a screening measurement based on a person’s weight relative to their height. It is commonly used as one way to categorize weight status in adults.

BMI does not directly measure body fat, muscle mass, or overall health. Therefore, it should be considered alongside other factors such as body composition, waist circumference, lifestyle, and individual health circumstances.

How to Use This BMI Calculator

Using the calculator is simple:

1. Enter your age.
2. Select your gender.
3. Choose Metric or Imperial units.
4. Enter your height and weight.
5. Click Calculate BMI.
6. Review your BMI score, category, estimated healthy weight range, and BMI Prime.

The calculator supports:

• Kilograms and centimeters
• Pounds, feet, and inches

How Is BMI Calculated?

For adults, BMI is calculated by dividing weight in kilograms by height in meters squared.

Metric formula

BMI = Weight (kg) ÷ Height² (m)

For example, a person weighing 70 kg and measuring 1.70 m tall would have:

70 ÷ (1.70 × 1.70) = 24.2

Their BMI would be approximately 24.2.

For Imperial units, the calculator uses weight in pounds and height in inches:

BMI = (Weight (lb) × 703) ÷ Height² (in)

These categories are commonly used for adults aged 20 and older. BMI is a screening measure and should not be interpreted as a diagnosis.

What Is the Healthy Weight Range?

The calculator estimates a weight range corresponding to a BMI between 18.5 and 24.9 for your height.

For example, if you are 170 cm tall, the estimated weight range associated with this BMI range is approximately 53.5–72.0 kg.

This is an estimate, not a personalized medical recommendation. Body composition, muscle mass, age, and other health factors can affect what is healthy for an individual.

What Is BMI Prime?

BMI Prime is calculated by dividing your BMI by 25, which is the upper boundary of the commonly used healthy BMI range for adults.

BMI Prime = BMI ÷ 25

For example:

BMI 24.2 ÷ 25 = 0.97

A BMI Prime below 1.0 indicates a BMI below 25. A value above 1.0 indicates a BMI above 25.

Limitations of BMI

BMI is useful as a general screening tool, but it has important limitations.

It does not distinguish between:

• Muscle and fat
• Bone mass and body fat
• Different patterns of fat distribution

For example, a muscular person may have a higher BMI because of increased muscle mass rather than excess body fat. BMI may also not provide a complete picture of health for every individual.

For children and teenagers, BMI is interpreted differently using age- and sex-specific growth charts and percentiles. This calculator is designed for adults aged 20 and older.

If you have concerns about your weight or health, consider speaking with a qualified healthcare professional.

Frequently Asked Questions