Free BMI Calculator
Use this free BMI Calculator to measure body mass index, estimate your healthy weight range, and understand whether your current weight falls into an underweight, normal weight, overweight, or obesity category.
Enter your height and weight below and click the button to calculate your BMI instantly.
What is BMI (Body Mass Index)?
Body Mass Index (BMI) is a simple measurement used to estimate whether a person's body weight is appropriate for their height. It is calculated using a formula that compares your weight to your height. Health professionals often use BMI as a quick screening tool to understand weight status and potential health risks related to underweight, overweight, or obesity.
Although BMI does not directly measure body fat, it provides a useful general indicator of body composition and overall weight category. Many doctors, fitness professionals, and health researchers use BMI to evaluate population health trends and identify possible weight-related health risks.
How Does This BMI Calculator Work?
This BMI calculator converts your height from centimeters into meters, squares the height value, and then divides your weight in kilograms by that number. The result is your BMI score.
After calculation, the tool also shows a BMI category so you can quickly understand the meaning of your score. This makes it useful for checking body weight status, healthy weight range, and general health screening in a simple way.
Why Use Our BMI Calculator?
- Instant body mass index result
- Clear BMI category explanation
- Simple height and weight inputs
- Works well on mobile and desktop
- Helpful for health, diet, and fitness tracking
BMI Formula
The standard BMI formula is:
BMI = weight (kg) ÷ height² (m²)
For example, if a person weighs 70 kilograms and has a height of 1.70 meters, the BMI is calculated by dividing 70 by 1.70 × 1.70.
BMI Scale Interpretation
After calculating your body mass index, it is important to understand what the result means. BMI values are grouped into weight categories that help estimate whether a person may be underweight, within a healthy weight range, overweight, or living with obesity.
BMI Categories Chart
Body Mass Index values are commonly grouped into categories to help interpret whether a person's body weight falls within a healthy range. These BMI ranges are widely used to estimate weight status and possible health risk levels.
| BMI Range | Weight Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal Weight |
| 25 – 29.9 | Overweight |
| 30 – 34.9 | Obesity Class 1 |
| 35 – 39.9 | Obesity Class 2 |
| 40 and above | Severe Obesity |
People with a BMI between 18.5 and 24.9 are generally considered to have a healthy body weight for their height. BMI values above 25 may indicate excess body weight, while a BMI of 30 or higher may suggest obesity and a higher risk of weight-related health conditions such as heart disease, diabetes, and metabolic disorders.
BMI Calculation Examples
Here are simple examples to understand how body mass index is calculated using height and weight.
Example 1: A person who weighs 70 kg and has a height of 170 cm (1.7 meters).
BMI = 70 ÷ (1.7 × 1.7) = 24.22
This result falls within the normal weight range.
Example 2: A person who weighs 90 kg and has a height of 180 cm (1.8 meters).
BMI = 90 ÷ (1.8 × 1.8) = 27.78
This result falls within the overweight range.
Limitations of BMI
Although BMI is widely used to estimate weight status, it does not directly measure body fat percentage. Body composition, muscle mass, bone density, and overall fitness level can influence BMI results.
For example, athletes or people with high muscle mass may have a higher BMI even though they have low body fat. Because of this, BMI should be considered a general health screening tool rather than a medical diagnosis.
Health professionals often combine BMI with other measurements such as waist circumference, body fat percentage, lifestyle factors, and medical history to get a more accurate picture of overall health.