Body Mass Index (BMI) Calculator

Calculate your BMI to assess if you're at a healthy weight for your height.

Calculator

Enter Your Measurements

Enter your weight in kilograms.

Enter your height in centimeters.

Overview

About BMI

Body Mass Index (BMI) is a numerical value derived from a person's weight and height. It provides a simple and objective measure that is commonly used to categorize individuals as underweight, normal weight, overweight, or obese.

History and Development

BMI was developed in the 1830s by Belgian mathematician and statistician Adolphe Quetelet. Originally called the "Quetelet Index," it was designed as a statistical tool to study the "average man" and not specifically for measuring body fat. In the 1970s, American physiologist Ancel Keys renamed it Body Mass Index and promoted its use for population studies on obesity.

Medical Applications

BMI is widely used in clinical settings and epidemiological studies for several reasons:

  • Screening tool for weight categories associated with health problems
  • Population-level assessment of obesity rates
  • Estimating disease risk related to weight
  • Practical method requiring only height and weight measurements

Global Standards and Variations

While the World Health Organization (WHO) has established standard BMI categories, there are recognized ethnic and population differences in body composition and health risks:

Regional Adaptations:
  • • Asian populations may have health risks at lower BMI thresholds
  • • Some countries have adopted modified BMI categories for their populations
  • • The relationship between BMI and health risk varies across ethnicities

Health Implications

Research has consistently shown associations between BMI categories and various health outcomes:

Underweight (BMI < 18.5)

  • • Nutritional deficiencies
  • • Weakened immune system
  • • Osteoporosis risk
  • • Fertility issues

Normal Weight (BMI 18.5-24.9)

  • • Lower risk of cardiovascular disease
  • • Lower risk of type 2 diabetes
  • • Improved mobility and energy
  • • Better overall health outcomes

Overweight (BMI 25-29.9)

  • • Increased risk of heart disease
  • • Higher blood pressure
  • • Risk of sleep apnea
  • • Joint problems

Obese (BMI 30+)

  • • Significantly higher cardiovascular risk
  • • Type 2 diabetes
  • • Certain cancers
  • • Respiratory issues

Scientific Basis

The relationship between BMI and health outcomes is supported by extensive research:

  • Large-scale epidemiological studies have found consistent connections between BMI and mortality rates
  • The Framingham Heart Study demonstrated links between BMI and cardiovascular disease
  • The Nurses' Health Study found correlations between BMI and various chronic diseases

Beyond the Number

While BMI is useful, it's important to remember that it's just one health indicator. For a comprehensive assessment, healthcare providers consider:

  • Waist circumference and waist-to-hip ratio
  • Body composition (muscle vs. fat percentage)
  • Family history and genetic factors
  • Physical activity levels and lifestyle factors
  • Blood pressure, cholesterol, and blood sugar levels
Concept

BMI Formula

Body Mass Index (BMI) is a measure of body fat based on height and weight that applies to adult men and women.

Formula:
BMI = weight (kg) / (height (m))²
Steps

How to Calculate BMI

To calculate your BMI, follow these steps:

  1. 1
    Measure your weight in kilograms
  2. 2
    Measure your height in meters
  3. 3
    Square your height (multiply it by itself)
  4. 4
    Divide your weight by your height squared

For example, if you weigh 70 kg and are 1.75 meters tall:

Example Calculation:
BMI = 70 / (1.75)² = 70 / 3.0625 = 22.86
Categories

BMI Categories

BMI categories are used to classify weight status and potential health risks:

Underweight

BMI less than 18.5

May indicate malnutrition or other health issues.

Normal weight

BMI 18.5 to 24.9

Generally associated with the lowest health risks.

Overweight

BMI 25 to 29.9

May increase risk of health problems.

Obese

BMI 30 or higher

Associated with increased health risks.

Important

BMI Limitations

While BMI is a useful screening tool, it has some limitations:

  • Does not account for muscle mass, bone density, or body composition
  • May not be accurate for athletes, pregnant women, or the elderly
  • Does not consider factors like age, sex, or ethnicity
  • Should be used as part of a comprehensive health assessment
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