BMI Calculator
Check Your Body Mass Index Instantly
Result
Healthy Weight for Your Height: -
BMI Prime: -
Ponderal Index: - kg/m³
Weight Suggestion: -
BMI Categories (WHO)
| Classification | BMI Range (kg/m²) |
|---|---|
| Underweight | < 18.5 |
| Normal Weight | 18.5 – 24.9 |
| Overweight | 25 – 29.9 |
| Obese Class I | 30 – 34.9 |
| Obese Class II | 35 – 39.9 |
| Obese Class III | ≥ 40 |
Features of Our BMI Calculator
Instant BMI Calculation
Get your Body Mass Index instantly by entering your height and weight.
Clear BMI Categories
Understand your result with clearly defined BMI categories, based on WHO data.
For Adults & Teens
Provides accurate classifications for adults and percentile-based results for teens.
Understand Health Risks
Learn about potential health risks associated with different BMI categories.
Transparent Formulas
We show you the exact formulas used, so you know how your result is determined.
Private and Secure
Your health data is your own. This tool works in your browser; we never store it.
Your Complete Guide to the BMI Calculator
What is BMI?
The Body Mass Index (BMI) is a measurement of a person’s leanness or corpulence based on their height and weight. It quantifies body tissue mass and is used as a general indicator of whether a person has a healthy weight for their height. Our free BMI Calculator gives you a quick and accurate assessment, helping you understand your result and what it means for your health.
BMI Categories for Adults
Your BMI result places you into one of several categories. The standard classifications published by the World Health Organization are as follows:
| Classification | BMI range (kg/m²) |
|---|---|
| Severe Thinness | < 16 |
| Moderate Thinness | 16 – 17 |
| Mild Thinness | 17 – 18.5 |
| Normal Weight | 18.5 – 25 |
| Overweight | 25 – 30 |
| Obese Class I | 30 – 35 |
| Obese Class II | 35 – 40 |
| Obese Class III | > 40 |
BMI for Children and Teens (Ages 2-20)
For children and teens, BMI is age- and sex-specific and is often referred to as BMI-for-age. The result is shown as a percentile ranking, which compares a child's BMI to others of the same age and sex.
| Category | Percentile Range |
|---|---|
| Underweight | Less than the 5th percentile |
| Healthy Weight | 5th percentile to less than the 85th percentile |
| At Risk of Overweight | 85th to less than the 95th percentile |
| Overweight | Equal to or greater than the 95th percentile |
Health Risks Associated with BMI
Being outside the "Normal Weight" range can increase the risk of certain health problems. It's one of many factors to consider for your overall health.
Being Overweight (BMI > 25)
An overweight BMI can increase the risk of conditions like Type 2 diabetes, high blood pressure, heart disease, stroke, and certain types of cancer.
Being Underweight (BMI < 18.5)
An underweight BMI can be associated with risks like malnutrition, vitamin deficiencies, a weakened immune system, and osteoporosis.
The Limitations of the BMI Calculator
While the BMI calculator is an excellent screening tool, it's important to understand its limitations. BMI does not directly measure body fat and does not distinguish between fat and muscle mass. Therefore, it may not be accurate for certain groups:
- Athletes: Bodybuilders and other highly muscular individuals may have a high BMI due to muscle mass, not excess fat.
- Age and Gender: Older adults tend to have more body fat than younger adults with the same BMI. Women typically have more body fat than men.
- Ethnic Variations: Body composition can vary among different ethnic groups.
For these reasons, the BMI result should be used as part of a larger conversation with a healthcare provider. After using our healthy weight calculator, you might consider our Body Fat Calculator for another perspective.
How to Calculate BMI: The Formula
Our calculator does the math for you, but if you're curious, here is the formula it uses:
For US Customary Units (pounds and inches):
BMI = (703 * 160) / (70 * 70) = 23.0
For Metric Units (kilograms and meters):
BMI = 72.57 / (1.778 * 1.778) = 23.0
Related Health Metrics
Beyond the standard Body Mass Index, other indices can provide additional insight.
BMI Prime
BMI Prime is a simple ratio of a person’s actual BMI to the upper limit of the "Normal" range (25 kg/m²). A value between 0.74 and 1.0 is considered normal.
Ponderal Index (PI)
The Ponderal Index is another measure of body composition that is sometimes considered more effective than BMI for very tall or very short individuals, as it cubes the height measurement rather than squaring it.
Conclusion
The Body Mass Index is a simple, valuable, and widely used method to get a general assessment of your body weight. However, it should always be considered alongside other factors such as body fat percentage, muscle mass, diet, and exercise habits. For personalized health advice, always consult with a doctor or registered nutritionist. Leading health authorities like the World Health Organization (WHO) provide excellent resources on maintaining a healthy lifestyle.
Frequently Asked Questions about Body Mass Index
How do I use the BMI calculator?
It's simple! Just enter your current height and weight into the fields of the BMI calculator above. You can use either metric (kilograms and meters) or US customary units (pounds and inches). The calculator will instantly show you your BMI number and which category you fall into on the BMI chart.
Is the BMI calculator accurate for everyone?
The Body Mass Index is a very reliable indicator of body fatness for the majority of the population. However, as mentioned, it may not be accurate for certain groups, such as bodybuilders, long-distance runners, pregnant women, the elderly, or children. It should be used as a general guide, not a definitive diagnostic tool.
What is considered a healthy BMI?
According to the World Health Organization, a Body Mass Index between 18.5 and 24.9 is considered to be in the healthy weight range for most adults. A result below 18.5 is classified as underweight, and a result of 25 or above is classified as overweight.
