BMI & Underweight Risk Calculator – Why This Tool Is Only a Screening Aid
This BMI & Underweight Risk Calculator is designed as an educational tool. It can give you a quick estimate of your body mass index (BMI) and show where that value sits in common adult BMI ranges, including underweight, healthy weight, overweight, and obesity.
How BMI Is Calculated
For adults, BMI is calculated using your height and weight:
or in imperial units:
Typical Adult BMI Categories
Many health organizations use ranges similar to:
- Underweight: BMI < 18.5
- Healthy weight: BMI 18.5–24.9
- Overweight: BMI 25–29.9
- Obesity: BMI ≥ 30
Some references also describe “severely underweight” at very low BMI values, but these are still screening thresholds, not a diagnosis of anorexia or any other eating disorder.
Why BMI Cannot Diagnose Anorexia Nervosa
Anorexia nervosa is a complex mental health condition involving thoughts, emotions, behaviours, and physical health. Diagnosis considers many factors, such as:
- Restrictive eating patterns and fear of gaining weight
- Body image concerns and distorted self-perception
- Physical signs like low weight, changes in vital signs, or nutritional deficiencies
- Impact on daily life, mood, and functioning
A BMI number alone cannot capture these factors. Very low BMI may signal a health risk, but only a qualified healthcare professional or mental health specialist can assess and diagnose an eating disorder.
If You Are Worried Your Weight or Eating
If you find yourself frequently checking your weight, fearing weight gain, skipping meals, or feeling distressed your body, it might help to talk with a doctor, dietitian, or therapist who understands eating disorders.
Using calculators and numbers can sometimes increase anxiety. If the results of this tool make you feel upset or overwhelmed, it may be a sign to focus less on numbers and more on getting supportive, human guidance.
Use BMI as One Small Piece of the Picture
BMI can be useful at a population level and as a quick screening tool, but it has important limitations. It does not directly measure health, fitness, or self-worth. A healthier approach is to look at the bigger picture: energy levels, mood, sleep, medical history, and guidance from healthcare professionals.
This calculator is for educational purposes only and is not a substitute for medical advice, diagnosis, or treatment. If you have concerns your weight, physical health, orationship with food, please reach out to a qualified health professional in your area.
You can explore more free tools on MyTimeCalculator for fitness, finance, health, math, and science, but always pair numbers with personalised advice when it comes to your body and well-being.