BMI Calculator — Healthy Weight Range (Free)
About This Tool
The BMI Calculator helps you determine your Body Mass Index, a widely used measure to assess whether you have a healthy body weight for your height. It works for both men and women and supports metric (kg/cm) and imperial (lbs/ft-in) units. The calculator also shows your healthy weight range and where you fall on the BMI scale.
How to Use
- Select your preferred unit system (Metric or Imperial)
- Enter your weight and height
- View your BMI, category, and healthy weight range instantly
Detailed Explanation & Worked Example
Body Mass Index (BMI)is a simple numerical calculation that estimates a person's body fat based on their height and weight. It is widely used by health and medical professionals to screen for underweight, normal weight, overweight, and obesity.
The Mathematical Formula for BMI
Depending on the system of measurement you use, the formula to calculate BMI is:
- Metric System:
BMI = weight (kg) / [height (m)]² - Imperial System:
BMI = [weight (lbs) / [height (in)]²] × 703
Step-by-Step Worked Example (Metric)
Let's calculate the BMI of an adult who weighs 70 kilograms and has a height of 175 centimeters (1.75 meters):
- First, convert height to meters squared:
1.75 × 1.75 = 3.0625 - Next, divide weight by height squared:
70 / 3.0625 = 22.86 - The resulting BMI is 22.9, which falls under the Normal weight category.
BMI Weight Classifications
According to the World Health Organization (WHO), the standard BMI categories for adults are:
- Underweight (BMI < 18.5): May indicate nutritional deficiencies or underlying health concerns.
- Normal Weight (BMI 18.5 – 24.9): Associated with the lowest risk of developing cardiovascular disease or diabetes.
- Overweight (BMI 25.0 – 29.9): Indicates moderate excess body weight and prompts lifestyle modifications.
- Obese (BMI ≥ 30.0): Indicates higher body fat levels and increased risk for chronic illnesses.