Find your body mass index, its WHO category and the healthy weight range for your height, in metric or US units.
BMI was devised in the 1830s by the Belgian statistician Adolphe Quetelet to describe populations, not to judge individuals. It’s still useful as a fast, free screening tool, but it has well-known blind spots. Here’s where it falls short and what to use alongside it.
Where BMI goes wrong
1. It can’t tell muscle from fat
BMI only knows your weight. A 180 cm rugby player weighing 95 kg has a BMI of 29.3, which counts as “overweight”, even at 12% body fat. Strength athletes, manual workers and very active people are often misclassified.
2. It ignores where fat is stored
Fat around the abdomen (visceral fat) is far more strongly linked to diabetes and heart disease than fat on the hips and thighs. Two people with the same BMI can carry very different risk.
3. Age changes body composition
After about 50, people tend to lose muscle and gain fat at the same weight (sarcopenia). An older adult with a “healthy” BMI may have a high body-fat percentage.
4. Ethnic differences
At the same BMI, people of South Asian, Chinese and some other Asian backgrounds tend to have more body fat and higher metabolic risk. That’s why several health bodies recommend lower thresholds; see BMI for Asian Adults: Why the Healthy Range Is Lower.
5. Sex differences
Women naturally carry more body fat than men at the same BMI.
6. Height extremes
Because height is squared, BMI slightly overestimates fatness in short people and underestimates it in very tall people.
Better companions to BMI
Waist circumference
Measure around your waist, midway between the lowest rib and the top of the hip bone, after breathing out.
| Increased risk | Substantially increased risk | |
|---|---|---|
| Men | above 94 cm (37 in) | above 102 cm (40 in) |
| Women | above 80 cm (31.5 in) | above 88 cm (35 in) |
Lower cut-offs (90 cm for men, 80 cm for women) are often used for South Asian adults.
Waist-to-height ratio (WHtR)
Divide your waist by your height, in the same units.
WHtR = waist ÷ height
The simple rule: keep your waist to less than half your height. A ratio below 0.5 is generally associated with lower risk across ages, sexes and ethnicities, which is why it’s increasingly recommended alongside BMI.
A person 170 cm tall with an 80 cm waist: 80 ÷ 170 = 0.47 ✓
Body-fat percentage
Measured with skinfold calipers, bioelectrical impedance scales, DEXA scans or a tape-measure formula. Typical healthy ranges are roughly 10–20% for men and 18–30% for women, varying with age. Home smart scales are convenient but can be off by several percentage points; focus on trends.
Waist-to-hip ratio
Waist ÷ hip circumference. Above 0.90 for men or 0.85 for women suggests central (abdominal) fat.
So should you ignore BMI?
No. For most people BMI correctly identifies weight status, and it costs nothing. The smart approach is:
- Calculate your BMI with the BMI calculator.
- Add waist-to-height ratio. It takes a tape measure and ten seconds.
- Interpret them together:
- BMI and WHtR both healthy → good sign.
- High BMI, WHtR under 0.5 → possibly muscular; probably low risk.
- Normal BMI, WHtR above 0.5 → worth attention (“normal weight central obesity”).
- Consider body-fat percentage if you train seriously.
Beyond body measurements
Blood pressure, blood sugar, cholesterol, fitness level and family history matter as much as any body measurement. If you’re making changes, start with sustainable energy intake (see How Many Calories Should I Eat to Lose Weight? A Realistic Guide) and talk to a healthcare professional for a full picture.
For the standard BMI categories and a healthy-weight chart, see What Is a Healthy BMI? Ranges, Charts and What Your Number Means.
Find your body mass index, its WHO category and the healthy weight range for your height, in metric or US units.