Anorexic BMI Calculator · Practical guide
BMI Thinness Categories Chart
The WHO defines three thinness levels below the healthy BMI range of 18.5 to 24.9.
At a glance
The WHO Thinness Categories
The World Health Organization divides underweight BMI into three thinness levels: mild thinness (17.0-18.49), moderate thinness (16.0-16.99), and severe thinness (below 16.0). The healthy or normal range begins at 18.5 and tops out at 24.9.
| Category | BMI Range | What It Means |
|---|---|---|
| Severe Thinness | Below 16.0 | Critically low weight; serious health risk possible |
| Moderate Thinness | 16.0 – 16.99 | Significantly underweight |
| Mild Thinness | 17.0 – 18.49 | Underweight |
| Normal Weight | 18.5 – 24.9 | Healthy range |
| Overweight | 25.0 – 29.9 | Above healthy range |
Interactive tool
Anorexic BMI Calculator
Enter your own values, then compare the result with the examples below.
Results
Example Readings
- 5'9" at 120 lb → BMI 17.7 — mild thinness
- 5'5" at 100 lb → BMI 16.6 — moderate thinness
- 5'5" at 90 lb → BMI 15.0 — severe thinness
- 5'7" at 105 lb → BMI 16.4 — moderate thinness
The same categories apply to men and women; only the height-weight combination changes the BMI value. Enter your own numbers above to see which band you land in, along with the healthy weight range for your height.
How These Cutoffs Are Used
Thinness categories are screening thresholds, not diagnoses. A reading in the moderate or severe band is a prompt to seek medical or nutritional evaluation, since early intervention improves outcomes for underweight conditions.
Frequently Asked Questions
Who created the BMI thinness categories?
The World Health Organization published these BMI cutoffs as a population screening standard for adults aged 18-65.
Is mild thinness the same as anorexia?
No. A low BMI is a screening signal only. Anorexia nervosa is a clinical diagnosis that involves behavior and psychology, not just a number.
Do the categories apply to athletes?
BMI does not account for muscle mass or body composition, so very lean athletes may score low without being unhealthy. Context and professional evaluation matter.
What BMI is considered normal?
The normal or healthy range is 18.5 to 24.9. Below 18.5 is underweight; 25 and above is overweight.