Underweight BMI & Risk Screening Calculator
Estimate BMI, underweight severity, and combined risk factors from symptoms and medical history. Educational guidance only — not a diagnostic tool.
Underweight BMI Assessment
Underweight BMI & Risk Screening Calculator
This tool estimates your Body Mass Index (BMI) and provides an educational overview of underweight categories along with a simple combined risk screening based on symptoms and medical history.
Important
This calculator is not a diagnostic tool and cannot detect or diagnose anorexia, other eating disorders, or any medical condition. It is for educational and informational purposes only. Only a qualified healthcare professional can provide a proper assessment.
If you are struggling with body image, disordered eating, or related concerns, please seek professional support.
How the Calculator Works
Inputs:
- Height and weight (metric or imperial)
- Age and biological sex
- Activity level
- Current symptoms (checkboxes)
- Medical history items (checkboxes)
Outputs:
- BMI value
- Underweight severity band (if applicable)
- Combined screening risk level (Low / Elevated / High / Critical)
- Healthy weight range corresponding to BMI 18.5–24.9
- Summary of selected symptoms and history
- Crisis resources when risk is elevated
BMI Underweight Categories Used
| BMI Range | Category |
|---|---|
| Below 15 | Life-threatening |
| 15 – 15.9 | Severe |
| 16 – 17.4 | Moderate |
| 17.5 – 18.4 | Mild |
| 18.5 and above | Not underweight |
Note: BMI has limitations. It does not account for muscle mass, bone structure, or individual health context. A normal BMI does not rule out health concerns, and a low BMI does not automatically mean an eating disorder.
Combined Risk Screening
The tool combines:
- BMI category
- Number and type of reported symptoms
- Medical history items
- Activity level
This produces a simple educational risk indicator (Low → Critical). It can also flag atypical patterns (for example, normal BMI with several concerning symptoms).
This is not a clinical assessment.
When to Seek Help
Please reach out for professional support if you experience:
- Persistent concerns about weight or body image
- Restrictive eating patterns
- Significant weight changes
- Loss of menstrual periods (in females)
- Dizziness, fatigue, or other physical symptoms
- Anxiety or distress related to food or exercise
Crisis & Support Resources
- 988 Suicide & Crisis Lifeline (US) – Call or text 988
- National Eating Disorders Association (NEDA) Helpline – 1-800-931-2237
- Crisis Text Line – Text HOME to 741741
- Emergency services – Call 911 if you are in immediate danger