The Body Mass Index (BMI) calculator is a valuable tool that assesses whether an individual is underweight, normal weight, overweight, or obese by considering both weight and height. This is important because weight alone can be misleading due to factors like body composition.

Calculating BMI:

To calculate BMI:

  1. Divide your weight (in kilograms) by your height (in meters).
  2. Divide the answer by your height again to get your BMI.

Expressed as a formula: BMI = weight / height².

Normal BMI:

BMI ranges are categorized as underweight, normal, overweight, and obese. A normal BMI falls within the range of 18.5-24.9. It’s important to note that BMI is a rough estimate and may not be accurate for individuals with high muscle mass or those who have lost significant muscle, such as the elderly.

For more precise assessments, specialized calculators like the body frame size calculator or skinfold body fat calculator can be considered.

BMI Ranges:

  1. Underweight: less than 18.5
  2. Normal weight: 18.5-24.9
  3. Overweight: 25-29.9
  4. Obesity: 30-35
  5. Severe obesity: 35 and over

BMI Prime:

BMI Prime is a useful modification, where 1.0 equals the upper limit of the normal BMI range. If BMI Prime is over 1, it indicates being overweight.

Using the BMI Calculator:

  1. Input your height and weight.
  2. Instantly obtain your BMI, BMI Prime, and corresponding range.

Adjusting Weight for a Healthy BMI:

If overweight and aiming for a healthy range, use the BMI Prime box by entering “0.9” to see the necessary weight loss.

Additional Considerations:

  • Metabolism Tracking: Utilize the basal metabolic rate calculator to gauge your body’s metabolism.
  • Ideal Weight: Determine your ideal weight using the ideal weight calculator.
  • Maintenance Calories: Calculate the calories needed to maintain your current weight with the maintenance calorie calculator.


  • Age and BMI: For adults, the normal BMI range is 18.5-24.9 and is not age-dependent. Children’s weight assessment considers age.
  • BMI for a Man Weighing 75 Kilos: Calculate BMI using weight and height; for instance, BMI = 75 / (height in meters)².

By understanding how to calculate BMI and considering additional factors, individuals can make informed decisions about their health and weight management. It’s essential to recognize the limitations of BMI and, when needed, explore more specialized tools for a comprehensive assessment of body composition and health.