The BMI Calculator helps you calculate your Body Mass Index using your height and weight. It gives your BMI score, weight category, healthy weight range, BMI Prime and Ponderal Index in one place.
This free online BMI calculator supports metric units and US units. You can enter height in centimetres and weight in kilograms, or use feet, inches and pounds.
What is BMI?
BMI stands for Body Mass Index. It is a simple value calculated from a person’s height and weight. BMI is commonly used as a screening tool to estimate whether an adult is underweight, in a healthy weight range, overweight or in an obesity range.
BMI does not directly measure body fat. It should be used as a starting point, not as a complete medical diagnosis.
BMI Formula
The standard BMI formula for metric units is:
The BMI formula for US units is:
BMI Chart for Adults
| S.No | BMI Range | Weight Category |
|---|---|---|
| 1 | Below 18.5 | Underweight |
| 2 | 18.5 to less than 25 | Healthy Weight |
| 3 | 25 to less than 30 | Overweight |
| 4 | 30 to less than 35 | Obesity Class 1 |
| 5 | 35 to less than 40 | Obesity Class 2 |
| 6 | 40 or above | Obesity Class 3 |
How to Use the BMI Calculator
- Choose Metric Units or US Units.
- Enter your age and gender.
- Enter your height and weight.
- Click the Calculate BMI button.
- Check your BMI score, category, healthy weight range and visual BMI graph.
Example BMI Calculation
Suppose a person weighs 70 kg and has a height of 175 cm. First, convert height into metres: 175 cm = 1.75 m.
A BMI of 22.9 falls within the healthy weight range for most adults.
What is a Healthy Weight Range?
The healthy weight range shows the approximate weight range that may place your BMI between 18.5 and 24.9 for your height. This is useful because two people with different heights will have different healthy weight ranges.
For example, a taller person may have a higher healthy weight range than a shorter person. That is why this calculator shows your weight range based on your entered height.
What is BMI Prime?
BMI Prime compares your BMI with the upper limit of the healthy BMI range. It is calculated by dividing your BMI by 25.
A BMI Prime below 1 usually means the BMI is below the upper healthy limit. A BMI Prime above 1 means the BMI is above the upper healthy limit.
What is Ponderal Index?
Ponderal Index is another body measurement value that compares body weight with height cubed. It is sometimes used along with BMI to understand body build.
Unlike BMI, which uses height squared, Ponderal Index uses height cubed. This can make it useful when comparing people at very short or very tall height ranges.
BMI for Children and Teenagers
This calculator is mainly designed for adults. For children and teenagers aged 2 to 19 years, BMI is usually interpreted using age and gender-based percentile charts.
| S.No | Child/Teen BMI Percentile | Category |
|---|---|---|
| 1 | Below 5th percentile | Underweight |
| 2 | 5th to less than 85th percentile | Healthy Weight |
| 3 | 85th to less than 95th percentile | Overweight |
| 4 | 95th percentile or greater | Obesity |
Risks of High BMI
A high BMI may be linked with higher risk of health problems, especially when combined with other risk factors. These may include high blood pressure, type 2 diabetes, heart disease, sleep-related breathing problems, joint stress and other metabolic concerns.
However, BMI alone cannot confirm a health condition. A healthcare provider may also consider waist size, blood pressure, blood sugar, cholesterol, activity level and medical history.
Risks of Low BMI
A very low BMI may suggest that a person is underweight. Being underweight can sometimes be linked with poor nutrition, low energy, weakness, lower immunity, vitamin deficiency or other health concerns.
If your BMI is very low or your weight has changed quickly without a clear reason, it is better to speak with a qualified healthcare provider.
Limitations of BMI
BMI is useful, but it has limitations. It does not measure body fat directly. It also does not separate muscle, fat, bone and water weight.
For example, athletes and people with high muscle mass may have a high BMI even when their body fat is not high. Older adults may have different body composition even with the same BMI as younger adults.
For a better health assessment, BMI should be considered along with other factors such as waist measurement, physical activity, food habits, sleep, blood pressure, cholesterol and medical advice.
Why Use CalcuPortal BMI Calculator?
- Free online BMI calculation
- Metric and US unit support
- Instant BMI score and category
- Healthy weight range based on your height
- BMI Prime and Ponderal Index result
- Visual BMI graph for easy understanding
- No sign-up or installation required
- Works smoothly on mobile and desktop
Related Health Calculators
You can also try our Calorie Burn Calculator, Age Calculator, and Ideal Weight Calculator for related health and conversion needs.
Important Health Note
This BMI calculator is for general information only. It should not replace professional medical advice, diagnosis or treatment. If your BMI is very low, very high or you have health concerns, speak with a qualified healthcare provider.