BMI Calculator

How It Works

1. 1

   Enter your measurements

   Choose metric or imperial units. Enter your height and weight.

2. 2

   View your BMI result

   See your calculated BMI value, weight category, and a visual indicator on the BMI scale.

3. 3

   Check your healthy range

   Review the ideal weight range for your height based on WHO guidelines. Consult a healthcare professional for personalized advice.

Understanding Body Mass Index

Body Mass Index (BMI) is the most widely used screening tool for classifying weight status in adults. Developed by Belgian mathematician Adolphe Quetelet in the 1830s and adopted by the World Health Organization (WHO), BMI is calculated by dividing a person's weight in kilograms by the square of their height in meters: BMI = kg/m². The WHO defines four primary categories: underweight (BMI < 18.5), normal weight (18.5–24.9), overweight (25.0–29.9), and obese (≥ 30.0). While BMI is an efficient population-level screening tool used in clinical settings worldwide, it has well-documented limitations. It does not distinguish between lean muscle mass and fat tissue — meaning athletes with high muscle mass may be classified as overweight despite having low body fat. It also does not account for differences in fat distribution, age, sex, or ethnicity. Our calculator supports both metric (cm/kg) and imperial (feet-inches/pounds) input modes, displays the exact BMI category with color-coded visual feedback, and shows the healthy weight range for your height.

Common pitfalls

• BMI flags muscular bodies as overweight. A 6-foot, 200 lb NFL running back computes to BMI 27.1, well into the overweight range. The cutoffs were built from 19th-century population data, not individual body composition. Waist circumference and body fat percentage catch what BMI misses.

• Children and teens need CDC growth-chart percentiles, not the adult 18.5/25/30 cutoffs. A BMI of 22 is normal for a 45-year-old woman and a red flag for a 10-year-old boy. Use CDC pediatric percentile charts below age 20.

• Asian populations face elevated diabetes and cardiovascular risk at lower BMI thresholds. The WHO 2004 expert consultation (Lancet 363:157) recommends 23 as an overweight cutoff and 27.5 as obese for many Asian populations, not the standard 25/30.

• BMI does not distinguish visceral from subcutaneous fat. Two people with BMI 28 can have different cardiovascular risk depending on where the fat sits. Waist-to-height ratio above 0.5 is a better single predictor of cardiovascular risk than BMI alone.

• Weight loss that preserves muscle can leave BMI unchanged even while waist measurement drops and blood pressure falls. Don't use BMI as your only progress metric. Waist circumference, resting heart rate, and blood pressure track the health outcomes that matter.

Frequently Asked Questions

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