BMI Calculator

Q: What formula does this BMI calculator use?

This calculator uses the standard WHO formula: BMI = weight in kilograms divided by height in meters squared. For imperial units (pounds and inches), the formula used is: BMI = (weight in pounds × 703) ÷ height in inches squared.

Q: Does BMI differ for men and women?

The BMI formula itself is the same for men and women. However, the interpretation can differ slightly since women naturally have a higher body fat percentage than men at the same BMI. Some health professionals use additional metrics for a fuller picture.

Q: How can I lower my BMI?

BMI can be reduced by losing body fat through a combination of a calorie-controlled diet and regular physical activity. A sustainable deficit of 300–500 calories per day typically leads to healthy weight loss of 0.5–1 lb per week.

Weight (kilograms)

Height (cm)

Sex (for context)

Your BMI

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Body Mass Index

What is BMI?

Body Mass Index (BMI) is a simple numerical measure of a person's weight relative to their height. It was developed in the early 19th century by Belgian mathematician Adolphe Quetelet and is now widely used by health organizations worldwide, including the World Health Organization (WHO), as a quick screening tool for weight categories.

BMI does not directly measure body fat, but research shows it correlates with more direct measures of body fat in most adults. It's best understood as a starting point — not a complete health picture.

BMI Formula Used

Metric: BMI = weight (kg) ÷ height² (m²)

Imperial: BMI = (weight (lbs) × 703) ÷ height² (inches²)

Both formulas produce the same result and are consistent with WHO and NIH standard methodology.

BMI Categories (WHO Standard)

BMI Range	Category	Status
Below 18.5	Underweight	Below healthy
18.5 – 24.9	Normal weight	Healthy range
25.0 – 29.9	Overweight	Above healthy
30.0 – 34.9	Obese Class I	High risk
35.0 – 39.9	Obese Class II	Very high risk
40.0 and above	Obese Class III	Extremely high risk

Limitations of BMI

BMI is a useful population-level tool but has known limitations:

Muscle mass: Athletes or highly muscular individuals may show a high BMI without carrying excess body fat.

Age and sex: Older adults tend to have more body fat at the same BMI. Women naturally carry more fat than men at equivalent BMI values.

Ethnicity: Some studies suggest that Asian populations may face health risks at lower BMI thresholds. Always consider your full health profile.

💡 Pro tip: Use BMI alongside waist circumference and other metrics for a more complete picture of your health. A waist measurement above 35 inches (women) or 40 inches (men) indicates higher cardiovascular risk regardless of BMI.

How to Improve Your BMI

If your BMI falls outside the healthy range, small sustainable changes work best. A calorie deficit of 300–500 kcal/day combined with regular physical activity (150+ minutes of moderate exercise per week, per WHO guidelines) can lead to healthy, steady weight loss of 0.5–1 lb per week without extreme restriction.

Frequently Asked Questions

What is a healthy BMI range?

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According to WHO guidelines, a BMI between 18.5 and 24.9 is considered normal or healthy weight for adults. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is classified as obese.

Is BMI accurate for everyone?

BMI is a useful population-level screening tool, but it has limitations. It does not distinguish between muscle and fat, so athletes or very muscular individuals may have a high BMI without excess body fat. It is best used alongside other health metrics.

What formula does this BMI calculator use?

This calculator uses the WHO-standard formula: BMI = weight (kg) ÷ height² (m²). For imperial units, the formula is: BMI = (weight in lbs × 703) ÷ height in inches². Both are equivalent and accepted worldwide.

Does BMI differ for men and women?

The BMI formula is the same for both. However, the interpretation differs slightly since women naturally carry a higher body fat percentage than men at the same BMI value. Some clinicians use sex-specific body fat thresholds alongside BMI.

How can I lower my BMI?

BMI is reduced by losing body fat through a calorie-controlled diet and regular exercise. A sustainable deficit of 300–500 calories per day typically leads to healthy weight loss of 0.5–1 lb per week. Use our TDEE calculator to find your personal calorie target.