BMI

The BMI (Body Mass Index) Calculator is a clean health tool designed to estimate your body mass category from your height and weight. By supporting both metric and imperial measurements, it determines your BMI score and displays where it falls within the standard World Health Organization (WHO) weight categories.

BMI is a widely used screening tool to evaluate body weight relative to height. While it does not measure body fat directly, it is a simple, non-invasive indicator that correlates with health outcomes in broad populations. This calculator provides a quick baseline to help you understand your weight profile.

All calculations run locally in your web browser, ensuring your health details remain private. No height, weight, or personal data is sent to external servers or tracked online. It is a secure, fast, and completely free health resource.

What this BMI calculator determines

This calculator calculates your Body Mass Index score and presents your weight classification according to standard medical guidelines. The primary result is your BMI value, which is rounded to one decimal place.

The results display your weight category, including underweight (BMI under 18.5), normal weight (18.5 to 24.9), overweight (25 to 29.9), and obese (30 or higher). These standard categories are recognized by health organizations worldwide, providing a quick reference to evaluate if your weight is within a healthy range for your height.

The BMI formulas

The Body Mass Index is calculated using standard formulas based on your selected measurement system:

• Metric System: BMI = Weight (kg) ÷ [ Height (m) ]²
• Imperial System: BMI = [ Weight (lbs) ÷ [ Height (in) ]² ] × 703

These formulas normalize weight relative to height, allowing comparison of body mass profiles across different heights. The imperial factor of 703 translates pounds and inches into metric equivalents, ensuring matching results across both systems.

Worked calculation examples

Let us look at examples for both the metric and imperial measurement systems:

1. Metric Example: An adult weighing 70 kilograms and standing 1.75 meters tall.
   • Formula: 70 ÷ (1.75)² = 70 ÷ 3.0625 = 22.86
   • Result: 22.9 BMI (Normal Weight category).
2. Imperial Example: An adult weighing 160 pounds and standing 5 feet 10 inches (70 inches) tall.
   • Formula: (160 ÷ (70)²) × 703 = (160 ÷ 4,900) × 703 ≈ 0.03265 × 703 = 22.95
   • Result: 23.0 BMI (Normal Weight category).

When to use this BMI calculator

Use this calculator as a quick, general screening tool to evaluate if your weight is in proportion to your height. It is a helpful reference for adults beginning a fitness, nutrition, or weight management plan, providing a standardized benchmark to track progress alongside other health indicators.

Because it requires only basic height and weight measurements, it is a fast and accessible tool to use at home. It helps identify potential weight-related risks without requiring expensive clinic evaluations or body composition scans.

Important limitations of BMI

While BMI is a useful screening tool, it has significant limitations because it does not distinguish between muscle mass, bone density, water weight, and body fat. Because muscle is denser than fat, muscular individuals (such as athletes or bodybuilders) may have a high BMI that classifies them as "overweight" or "obese" despite having very low body fat.

Additionally, BMI does not account for age, gender, or ethnicity. Older adults often lose muscle and gain fat without their weight changing, which can hide health risks at a "normal" BMI. Do not use BMI as a definitive diagnosis; consult a healthcare professional for a complete health evaluation.

Frequently asked questions

Related tools

• Body Fat %
• Ideal Weight
• Calorie (TDEE)