Health

BMI Calculator

Calculate your Body Mass Index and healthy weight range.

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BMI Calculator

Unit System

Weight

Height

Results

Formula & Methodology

BMI = Weight (kg) / Height (m)²

Categories:
< 18.5: Underweight
18.5 – 24.9: Normal weight
25.0 – 29.9: Overweight
30.0 – 34.9: Obese (Class I)
35.0 – 39.9: Obese (Class II)
≥ 40.0: Obese (Class III)

About BMI Calculator

Body Mass Index (BMI) is a value derived from the mass (weight) and height of a person. It provides a simple numeric measure of body fat and is used to screen for weight categories that may lead to health problems.

BMI Limitations

While BMI is a useful screening tool, it has limitations. It does not account for muscle mass, bone density, age, or sex differences. Athletes may have a high BMI due to muscle, not fat.

Complete Guide

What Is BMI?

Body Mass Index (BMI) is a numerical measure derived from your height and weight. It was developed by Belgian mathematician Adolphe Quetelet in the 1830s and has been used in medicine and public health research for decades.

How to Calculate BMI

Metric: BMI = Weight (kg) / [Height (m)]²

Imperial: BMI = [Weight (lbs) × 703] / [Height (inches)]²

Example: 70 kg, 1.75 m tall:
BMI = 70 / (1.75)² = 70 / 3.0625 = 22.9 (Normal weight)

BMI Categories (WHO)

BMI Range	Category
Below 18.5	Underweight
18.5 – 24.9	Normal weight
25.0 – 29.9	Overweight
30.0 – 34.9	Obese (Class I)
35.0 – 39.9	Obese (Class II)
40.0 and above	Extremely Obese (Class III)

BMI for Asian Populations

Research shows that Asians have higher body fat percentage at the same BMI compared to people of European descent, with higher health risks at lower BMI values. Many health organizations recommend lower thresholds for Asian adults:

Overweight: ≥ 23 BMI (instead of 25)
Obese: ≥ 27.5 BMI (instead of 30)

Limitations of BMI

BMI is a useful population-level screening tool, but it has significant limitations when applied to individuals:

Doesn't measure body fat directly: A bodybuilder and an obese person can have the same BMI, despite very different body compositions.
Ignores fat distribution: Abdominal (visceral) fat is more dangerous than fat stored in the hips and thighs. Waist circumference is often a better predictor of metabolic risk.
Varies by age: Older adults with the same BMI as younger adults typically have more body fat. The healthy BMI range shifts slightly upward with age.
Differs by sex: Women naturally have higher body fat than men at the same BMI.

Better Metrics to Use Alongside BMI

Waist circumference: Risk increases above 80 cm (women) and 94 cm (men)
Waist-to-height ratio: Should be under 0.5 for most adults
Body fat percentage: Measured via DEXA scan, hydrostatic weighing, or bio-impedance
Blood tests: Blood sugar, cholesterol, triglycerides, and blood pressure are direct health markers

Use our BMI Calculator as a starting point, but always discuss your results with a healthcare professional for a complete picture of your health.

Frequently Asked Questions

BMI (Body Mass Index) is a measure of body fat based on height and weight. Formula: BMI = weight(kg) / height(m)². It provides a simple screening tool to categorize weight status, though it doesn't directly measure body fat percentage.

WHO BMI categories: Underweight < 18.5, Normal weight 18.5–24.9, Overweight 25–29.9, Obese Class I 30–34.9, Obese Class II 35–39.9, Obese Class III (Extreme) ≥ 40. Asian populations often use lower thresholds (e.g., overweight ≥ 23).

BMI doesn't account for muscle mass (athletes may be "overweight" by BMI), fat distribution, age, sex, or ethnicity. A muscular person and an obese person can have the same BMI. It's a screening tool, not a diagnostic measure.

For most adults, a BMI of 18.5 to 24.9 is considered healthy. However, some studies suggest an optimal range of 22–23. For older adults (65+), a slightly higher BMI (25–27) may be associated with lower mortality risk.

For children and teens (2-18 years), BMI percentiles are used instead of fixed categories, since healthy BMI ranges vary by age and sex. Overweight is ≥ 85th percentile; obese is ≥ 95th percentile.

Use the imperial formula: BMI = (weight in lbs × 703) / (height in inches)². Or convert: 1 kg = 2.205 lbs, 1 meter = 3.281 feet. Our calculator handles both metric and imperial inputs.

Lower BMI through a caloric deficit (eat less than you burn), regular exercise (both cardio and strength training), adequate sleep, and stress management. Even a 5-10% weight loss in overweight individuals significantly reduces health risks.

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