Understanding Body Mass Index.
A guide to understanding what BMI is, how it works, and what it means for your health.
Calculate your BMI.
What is BMI?
Body Mass Index (BMI) is a numerical value calculated from a person's weight and height. It provides a simple screening tool to categorize individuals into weight categories that may indicate health risks. BMI is calculated by dividing a person's weight in kilograms by the square of their height in meters.
BMI Formula
Metric: BMI = weight (kg) / height (m)2
BMI Categories
Underweight
Below 18.5
May indicate nutritional deficiency or other health issues. Consult with a healthcare provider.
Normal weight
18.5 - 24.9
Generally associated with a lower risk of weight-related health conditions.
Overweight
25.0 - 29.9
May increase risk for certain health conditions. Lifestyle changes may be beneficial.
Obese
30.0 and above
Associated with higher risk for heart disease, type 2 diabetes, and other conditions. Medical guidance is recommended.
Limitations of BMI.
While BMI is a useful screening tool, it has important limitations. BMI does not directly measure body fat, and it does not account for factors like muscle mass, bone density, age, sex, or ethnicity.
A person with high muscle mass (like an athlete) may have a high BMI but low body fat. Conversely, an older adult with less muscle may have a normal BMI but a higher percentage of body fat.
BMI should be used as a starting point for health assessment, not as a definitive diagnosis. Your healthcare provider can perform additional assessments to evaluate your overall health risk.
Important Exclusions
Standard adult BMI categories should not be used for:
- Children and teens:BMI for individuals under 20 is age- and sex-specific and uses percentile charts, not the adult categories listed above.
- Pregnant women:Weight gain during pregnancy is expected and healthy. BMI calculations during pregnancy do not accurately reflect health status.
What does BMI mean for weight loss?
If your BMI indicates that you are overweight or obese, structured weight loss under medical supervision can significantly improve your health outcomes. Even a modest reduction in BMI, equivalent to losing 5-10% of your body weight, has been shown to reduce risk factors for heart disease, diabetes, and other chronic conditions.
Programs like ShiftSetGo combine medically formulated nutrition with one-on-one coaching to help members achieve and maintain a healthier BMI through sustainable habits, not crash diets.
Concerned about your BMI?
A free consultation with a ShiftSetGo coach can help you understand your options and create a plan that works for your body and your life.