The "Keep It Under 0.5" Rule
Dr. Margaret Ashwell's research has highlighted a critical flaw in BMI: it doesn't account for where fat is stored. Central obesity (belly fat) is far more dangerous than fat stored on the hips or thighs.
Why 0.5?
Studies involving over 300,000 people have shown that keeping your waist circumference to less than half your height increases life expectancy for all people, regardless of gender, age, or ethnicity. It is a powerful predictor of diabetes, hypertension, and cardiovascular disease risk.
Why This Beats BMI
The Bodybuilder Problem
A 6ft athlete with significant muscle mass and a tight 32-inch waist might be classified as "Overweight" by BMI standards. The WHtR calculator correctly identifies them as Healthy (0.44).
The "Skinny Fat" Problem
A person with normal weight but a larger belly (visceral fat) might have a "Healthy" BMI but be at high risk for heart disease. WHtR correctly identifies the risk.
Ashwell Shape Chart Standards
| Category | Ratio | Message |
|---|---|---|
| Extremely Slim | < 0.40 | Take Care (Possible Underweight) |
| Healthy | 0.40 - 0.49 | OK (Lower Risk) |
| Overweight | 0.50 - 0.59 | Consider Action |
| Obese | ≥ 0.60 | Take Action |
Related Health Tools
Compare your results with other standard metrics.
Frequently Asked Questions
What is the String Test?
Does age matter for waist-to-height ratio?
Is WHtR better than BMI?
What if my ratio is over 0.6?
Tools & Data Verified by the EverydayCalculators Medical Research Team.
Last updated: December 2026.