How to Calculate BMI
Body Mass Index (BMI) is a simple calculation using height and weight. While not a direct measure of body fat, it is a useful screening tool to identify potential weight-related health risks.
BMI Formula
Metric: BMI = weight (kg) / height (m)^2
Imperial: BMI = (weight (lbs) x 703) / height (inches)^2
BMI Categories
| BMI Range | Category |
|---|---|
| Below 16 | Severe Underweight |
| 16 - 18.4 | Underweight |
| 18.5 - 24.9 | Normal Weight |
| 25 - 29.9 | Overweight |
| 30 - 34.9 | Obesity Class I |
| 35 - 39.9 | Obesity Class II |
| 40+ | Obesity Class III |
How to Use This Calculator
- Select your unit system (metric or imperial)
- Enter your weight (in kg or lbs)
- Enter your height (in cm or inches)
- Click Calculate to see your BMI, category, and healthy weight range
Beyond BMI: Other Health Indicators
While BMI is useful, consider these additional measures for a more complete health picture:
- Waist circumference: Men over 40 inches and women over 35 inches have higher health risks
- Body fat percentage: A more direct measure of body composition
- Waist-to-hip ratio: Indicates fat distribution patterns
- Blood pressure, cholesterol, and blood sugar: Direct health markers
BMI Calculator FAQ
What is BMI?
BMI (Body Mass Index) is a measure that uses your weight and height to estimate whether you are at a healthy weight. It is calculated by dividing your weight in kilograms by your height in meters squared (kg/m2). BMI is a screening tool, not a diagnostic measure.
What is a healthy BMI range?
A BMI of 18.5 to 24.9 is considered healthy weight. Below 18.5 is underweight, 25-29.9 is overweight, and 30 or above is obese. However, BMI does not account for muscle mass, bone density, or body composition.
Is BMI accurate for athletes?
BMI can overestimate body fat in athletes and muscular individuals because muscle weighs more than fat. A bodybuilder with low body fat may have a "overweight" BMI. For athletes, body fat percentage or waist-to-hip ratio may be better indicators.
Does age affect BMI interpretation?
For adults over 65, a slightly higher BMI (25-27) may actually be associated with better health outcomes. For children and teens, BMI is interpreted using age- and sex-specific percentiles rather than fixed thresholds.
What are the limitations of BMI?
BMI does not distinguish between fat and muscle, does not account for fat distribution (visceral vs. subcutaneous), and may not be accurate for different ethnic groups. It is best used as a starting point alongside other health indicators.