What Is BMI Calculator? Complete Guide 2026

Body Mass Index (BMI) is a widely used health indicator that helps estimate whether a person has a healthy body weight for their height. It is calculated using a simple formula: BMI = weight (kg) / height (m²). This makes BMI an easy and quick way to assess general health risks related to weight.

Although BMI does not directly measure body fat, it provides a useful starting point for understanding weight categories and potential health concerns.

How to Calculate BMI

Calculating your BMI is straightforward. Use the formula that matches your preferred measurement system:

1. Metric Formula:
Divide your weight in kilograms by your height in meters squared:
BMI = kg / m²

2. Imperial Formula:
Divide your weight in pounds by your height in inches squared, then multiply the result by 703:
BMI = (lbs / inches²) × 703

Using a BMI calculator makes this process even faster and helps avoid manual calculation errors.

BMI Categories

BMI values fall into different categories that indicate whether your weight is within a healthy range:

• Underweight: BMI less than 18.5
• Normal Weight: BMI 18.5 to 24.9
• Overweight: BMI 25 to 29.9
• Obese: BMI 30 or higher

These categories help identify potential health risks such as nutritional deficiency, heart disease, or obesity-related issues.

Limitations of BMI

While BMI is a useful screening tool, it also has some important limitations. It does not differentiate between muscle mass and fat mass. For example, athletes or bodybuilders may have a high BMI due to muscle but still be perfectly healthy.

Similarly, older adults or individuals with low muscle mass may have a “normal” BMI even if their body fat percentage is high. Because of this, BMI should be used as an initial indicator rather than a complete health assessment.

For a more accurate understanding of your health, always consider additional measurements such as body fat percentage, waist circumference, and professional medical evaluation.