Metric formula
BMI = weight (kg) / height (m)^2. For example, if someone weighs 68 kg and is 1.72 m tall, the BMI is 68 / 1.72^2.
How-To Guide
How to Calculate BMI Manually
BMI is a fast screening ratio based on weight and height. The arithmetic is easy, but the result should be interpreted alongside other health markers rather than in isolation.
4 min read Updated 2026年4月7日
Quick steps
- In metric units, divide weight in kilograms by height in meters squared.
- In imperial units, multiply weight in pounds by 703 and divide by height in inches squared.
- Round the result to about one decimal place.
- Use the number as a reference point, not a full health diagnosis.
Imperial formula
BMI = weight (lb) x 703 / height (in)^2. If height is split into feet and inches, convert it to total inches first.
How to read the result carefully
BMI is useful for a quick screen, but it does not capture everything about body composition or overall health.
- People with more muscle can look overweight by BMI alone
- Waist size, body fat, age, and sex still matter
- Health decisions should use clinical or professional guidance when needed
Frequently Asked Questions
Does a normal BMI always mean someone is healthy?expand_more
No. BMI is only one screening signal and should be read with other measures such as blood pressure, body fat, and lifestyle patterns.
Can I use centimeters directly in the metric formula?expand_more
Not directly. Convert centimeters to meters first, then square the height value.
Is BMI accurate for very athletic people?expand_more
Not always. Higher muscle mass can push BMI upward even when body fat is not high.
Try the BMI calculator
Switch between metric and imperial units, then check BMI, category, and healthy weight range in one place.
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