Calculate your Body Mass Index (BMI)
What Is BMI?
BBMI, or Body Mass Index, is the value this BMI calculator computes from your height and weight. It provides a simple, widely used screening tool to categorize body weight relative to height — helping to identify whether a person is underweight, at a healthy weight, overweight, or obese. BMI is used by healthcare professionals worldwide as a quick first indicator of potential weight-related health risks.
It’s important to understand that BMI is a screening tool, not a diagnostic measure. It does not directly measure body fat, and factors like muscle mass, bone density, age, and sex can affect its accuracy. Always consult a healthcare provider for a full health assessment.
How Does a BMI Calculator Compute Your Result?
The BMI formula is straightforward. It divides your weight by the square of your height:
Imperial: BMI = 703 × weight (lbs) ÷ height (in)²
Example (metric): 70 kg ÷ (1.75 m)² = 70 ÷ 3.0625 = 22.9
Example (imperial): 703 × 154 lbs ÷ (69 in)² = 108,262 ÷ 4,761 = 22.7
Our BMI calculator handles both metric and imperial units automatically — just switch between tabs and enter your numbers.
BMI Categories — What Do the Numbers Mean?
The World Health Organization (WHO) defines the following BMI categories for adults:
| BMI Range | Category | Health Implication |
|---|---|---|
| Below 18.5 | Underweight | May indicate nutritional deficiency or other health issues |
| 18.5 – 24.9 | Normal weight | Associated with the lowest risk of weight-related health problems |
| 25.0 – 29.9 | Overweight | Slightly elevated risk of cardiovascular and metabolic conditions |
| 30.0 – 34.9 | Obese (Class I) | Increased risk of type 2 diabetes, heart disease, and other conditions |
| 35.0 – 39.9 | Obese (Class II) | High risk — medical consultation strongly recommended |
| 40.0 and above | Obese (Class III) | Very high risk — also referred to as severe or morbid obesity |
BMI for Men vs. Women — Is There a Difference?
The standard BMI formula is the same for men and women, but the interpretation can differ slightly. Women naturally tend to have a higher body fat percentage at the same BMI compared to men, due to differences in body composition. Some researchers suggest that health risk thresholds may differ slightly by sex, but the WHO categories remain the standard reference used in most clinical settings.
BMI for Children and Teenagers
BMI for children and teens (ages 2–19) is calculated differently from adult BMI. Instead of fixed thresholds, it is compared against age- and sex-specific growth charts. A child’s BMI result is expressed as a percentile relative to other children of the same age and sex. Our calculator is designed for adults (age 18+).
Limitations of BMI
While BMI is a useful and widely accessible screening tool, it has well-documented limitations:
It doesn’t measure body fat directly
BMI cannot distinguish between fat mass and muscle mass. A highly muscular athlete may have a BMI in the „overweight“ range despite having very low body fat. Conversely, someone with a „normal“ BMI may carry a high proportion of body fat.
It doesn’t account for fat distribution
Where fat is stored matters for health. Abdominal (visceral) fat is associated with higher cardiovascular and metabolic risk than fat stored in the hips and thighs. BMI gives no information about fat distribution.
Age and ethnicity affect accuracy
Older adults may have more body fat at the same BMI as younger adults. Some ethnic groups — particularly people of Asian descent — face elevated health risks at BMI thresholds lower than the standard WHO cut-offs.
Frequently Asked Questions
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