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What is BMI (Body Mass Index)?

BMI (Body Mass Index) is a measure used to determine whether a person's weight is ideal, underweight, or overweight based on their height. BMI is calculated by dividing weight in kilograms by the square of height in meters (kg/m²). This method is widely used by health professionals worldwide as an initial indicator of nutritional status.

BMI Calculation Formula

BMI = Body Weight (kg) ÷ Height² (m²)Formula: BMI = Weight (kg) ÷ (Height (m) × Height (m))

Variables:

  • BMIBody Mass Index (kg/m²)
    Body Mass Index (kg/m²)(e.g.: 24.5)
  • Body WeightBody weight in kilograms
    Body weight in kilograms(e.g.: 70 kg)
  • HeightHeight in meters
    Height in meters(e.g.: 1.70 m)

Categories:

< 18.5Underweight
18.5 - 24.9Normal Weight
25.0 - 29.9Overweight
≥ 30.0Obesity

How to Use the KalkuLab BMI Calculator

  1. 1

    Enter Your Weight

    Weigh yourself and enter the value in kilograms (kg). For best accuracy, weigh yourself in the morning before eating.

  2. 2

    Enter Your Height

    Measure your height and enter it in centimeters (cm). Stand straight without shoes for accurate measurement.

  3. 3

    View Your Result

    Your BMI is calculated automatically using the standard WHO formula.

  4. 4

    Check Your Category

    See your BMI category (underweight, normal, overweight, or obesity) with color-coded explanation.

Examples

Example 1: Fitness Athlete with Ideal Weight

Problem:

Budi is a fitness athlete in Jakarta weighing 70 kg with a height of 175 cm. What is his BMI?

Solution:
  1. 1.Convert height to meters: 175 cm = 1.75 m
  2. 2.Calculate height squared: 1.75 × 1.75 = 3.0625 m²
  3. 3.Calculate BMI: 70 ÷ 3.0625 = 22.86
Result:22.86

BMI 22.86 falls into the 'Normal Weight' category (18.5 - 24.9). Ideal for a fitness athlete looking to maintain performance.

Example 2: Homemaker Starting a Diet

Problem:

Mrs. Siti, a homemaker weighing 68 kg with a height of 158 cm, wants to start a healthy diet program. What is her BMI?

Solution:
  1. 1.Convert height to meters: 158 cm = 1.58 m
  2. 2.Calculate height squared: 1.58 × 1.58 = 2.4964 m²
  3. 3.Calculate BMI: 68 ÷ 2.4964 = 27.24
Result:27.24

BMI 27.24 falls into the 'Overweight' category (25 - 29.9). Mrs. Siti is advised to lose 5-8 kg to achieve an ideal BMI.

Frequently Asked Questions

What is a normal BMI?
A normal BMI ranges from 18.5 to 24.9 according to WHO standards.
Is BMI accurate for athletes?
BMI may overestimate body fat in muscular athletes because it does not distinguish muscle from fat mass.
How often should I check my BMI?
Check monthly if you are actively managing weight, or every 3-6 months for general health monitoring.

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References