BMI Calculator

What is BMI (Body Mass Index)?

Body Mass Index (BMI) is a number calculated from a person’s weight and height. It is used as a simple screening tool to estimate whether a person is underweight, a healthy weight, overweight, or living with obesity. BMI does not measure body fat directly, but it is widely used because it provides a quick, consistent way to evaluate weight status.

How to Calculate BMI

BMI can be calculated using two systems depending on the units you choose in this calculator:

Metric Formula (kg/cm):

BMI = weight (kg) ÷ height (m)²

For example, if your weight is 70 kg and your height is 1.75 m, the BMI would be:

BMI = 70 ÷ (1.75 × 1.75) = 22.86.

US Units Formula (lbs/in):

When using pounds and inches, BMI is often calculated using a constant multiplier (703) to adjust the units:

BMI = (weight (lbs) ÷ (height (in) × height (in))) × 703.

This calculator automatically handles the conversion between metric and US units.

BMI Categories and Weight Status

Once your BMI is calculated, it’s compared to standard adult categories to help interpret your result:

BMI Category BMI (kg/m²) Severe Thinness < 16 Moderate Thinness 16 – 17 Mild Thinness 17 – 18.5 Normal (Healthy Weight) 18.5 – 25 Overweight 25 – 30 Obesity Class I 30 – 35 Obesity Class II 35 – 40 Obesity Class III > 40 These categories are widely used in clinical settings to assess whether a person’s weight might be putting their health at risk.

Why BMI Matters

Understanding “what is BMI” and “BMI meaning” is helpful because your BMI score can indicate potential health risks:

• A higher BMI is associated with increased risk of conditions such as heart disease, high blood pressure, type 2 diabetes, and other metabolic problems.
• A lower than normal BMI may indicate undernutrition or other health concerns.

However, BMI is a screening tool only. It does not measure body fat directly, and factors such as muscle mass, bone density, and body composition are not included in the calculation.

Understanding Your Results

Healthy BMI range: Most health institutions consider a BMI between 18.5 and 25 kg/m² to be a normal, healthy range.

Healthy weight for your height:

Based on your height, there’s a range of weight that typically falls within the healthy BMI category. This calculator gives you that range to help you understand where your current weight stands relative to recommended healthy standards.

BMI Prime: This is another number derived from BMI that compares your BMI value to the upper limit of the healthy range (25). A BMI Prime above 1.0 suggests overweight status relative to healthy cutoffs.

Ponderal Index: A less common measure similar to BMI that takes height cubed into account, useful in some clinical and research settings.

How to Use the BMI Calculator

1. Enter your age, height, and weight in your preferred units (Metric or US).
2. The calculator will update automatically with your BMI result, category, and interpretation.
3. Review your BMI category to understand your general weight status.
4. Read accompanying tips related to your result to help with health planning or lifestyle changes.

Tips After Getting Your BMI

• If your BMI is in the normal range (18.5 – 25), maintain balanced nutrition and regular physical activity.
• If your BMI indicates overweight or obesity, consider consulting health professionals for personalized advice on diet and exercise.
• If your BMI is below normal, discuss safe weight gain options with a healthcare provider.