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BMI Calculator

Calculate your Body Mass Index instantly. Get your BMI value and WHO health classification.

How to Use the BMI Calculator

Choose metric (kg/cm) or imperial (lb/in), enter your weight and height, then click “Calculate BMI”. The result shows your BMI value plus the WHO category — underweight, normal, overweight or obese — so you can see where you stand at a glance.

BMI is a screening tool, not a diagnosis. Athletes with high muscle mass often score high, and older adults may be healthy at a slightly higher BMI. Use it to track long-term trends, and always combine it with waist circumference or a doctor’s advice for a full picture.

For children and teenagers, BMI is interpreted using age- and sex-specific percentiles, not the adult ranges shown here. If your BMI falls outside the normal range, focus on sustainable habits - balanced meals, regular movement and enough sleep - rather than crash dieting.

Track your BMI monthly rather than daily - daily fluctuations from water weight are normal and misleading. Pair the number with simple measurements like waist size to see a fuller picture, and consult a healthcare professional if you plan major changes.

About This BMI Calculator

Body Mass Index (BMI) is a screening tool that estimates body fat based on height and weight. It's calculated by dividing weight in kg by height in meters squared. While not a perfect health metric, it's a useful starting point for understanding weight-related health risks.

Limitations: BMI doesn't account for muscle mass, bone density, or fat distribution. Athletes and older adults should use it as a rough guide, not a diagnosis.

BMI Categories (WHO Standard)

< 18.5
Underweight
18.5–24.9
Normal
25–29.9
Overweight
≥ 30
Obese

How to Use

  1. Select your preferred unit system (metric or imperial)
  2. Enter your weight and height
  3. Click Calculate to see your BMI value and category

Frequently Asked Questions

What is BMI?

Body Mass Index (BMI) is a screening tool that estimates body fat based on height and weight. It's calculated as weight (kg) divided by height squared (m²).

Is BMI accurate for athletes?

BMI may overestimate body fat in athletes with high muscle mass and underestimate it in older adults with low muscle mass. Use it as a general guide.

What's a healthy BMI?

A BMI between 18.5 and 24.9 is considered the healthy range by WHO standards. Below 18.5 is underweight, 25–29.9 is overweight, and 30+ is obese.

Is my data stored or sent anywhere?

No. All calculations happen entirely in your browser. Nothing is sent to any server.