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Body Mass Index,
in plain numbers.
Type your height and weight — see your BMI, your category on the WHO scale, and the exact weight range that lands you in the healthy band. Metric or U.S. units, your call.
Inputs
Body measurements
Optional context
- Healthy range
- 56.7–76.6 kg
- BMI Prime
- 0.94
- Ponderal idx
- 13.43 kg/m³
Body Mass Index
kg / m²
Healthy weight
56.7–76.6kg
For your height (175 cm)
Spectrum
12–42
Healthy band
Weight vs height (kg / cm)
Reference
WHO BMI categories (adults)
| Category | BMI | Weight (kg) |
|---|---|---|
| Severe thinness | < 16 | < 49 |
| Moderate thinness | 16–17 | 49–52.1 |
| Mild thinness | 17–18.5 | 52.1–56.7 |
| Normal weight | 18.5–25 | 56.7–76.6 |
| Overweight | 25–30 | 76.6–91.9 |
| Obese class I | 30–35 | 91.9–107.2 |
| Obese class II | 35–40 | 107.2–122.5 |
| Obese class III | ≥ 40 | ≥ 122.5 |
Field guide
What BMI actually measures.
Body Mass Index (BMI) is a single number relating your weight to your height. It was popularized in the 1970s as a quick public- health proxy for body fat, useful at the population level, imperfect at the individual level. It says nothing about muscle, bone, or fat distribution, only about mass-to-stature.
The formula
BMI is a straightforward division. The metric form is canonical; the U.S. form simply rescales it.
The categories (WHO, adults)
For adults aged 20 and over the World Health Organization defines the following bands. The same numbers are used worldwide, with additional Asia-Pacific cut-offs (overweight ≥ 23, obese ≥ 27.5) in some clinical settings.
- Underweight: BMI < 18.5
- Normal weight: 18.5 to 24.9
- Overweight: 25 to 29.9
- Obese class I: 30 to 34.9
- Obese class II: 35 to 39.9
- Obese class III: 40 and above
BMI Prime
BMI Prime is your BMI divided by 25 — the upper edge of the normal range. A value at or below 1.0 sits inside the healthy band; 1.20 means 20% above the normal ceiling. It's a useful one-glance way to see how far off the healthy band you are without doing the arithmetic yourself.
Where BMI breaks down
BMI was never designed for individual diagnosis. It can mislead in three predictable ways:
- Athletes & muscle. Lean, muscular people read as overweight; muscle is denser than fat, but the index can't see the difference.
- Older adults. Loss of bone density and muscle with age can put a person in the “normal” band while body fat is well above healthy levels.
- Children & teens. Growth changes the relationship between height and weight constantly; under age 20, clinicians use age- and sex-specific BMI percentiles, not the adult cut-offs.
Healthy weight range
For your specific height, the calculator above solves the formula in reverse: it returns the weight values that map onto BMI 18.5 (lower bound) and 25.0 (upper bound). That's your healthy band — the green band on the chart.
Worked example
A person 1.78 m tall weighing 76 kg has a BMI of 76 ⁄ 1.78² ≈ 24.0 — the high end of the normal range. To stay normal at that height, weight should be between roughly 58.6 and 79.2 kg — the band our calculator surfaces in the result panel.
How to use this number
Treat BMI as a starting point, not a verdict. If it nudges you to look more carefully at body composition, blood pressure, resting heart rate, fasting glucose, and waist circumference, you've used it well. If it labels a powerlifter “obese,” that's the index showing its limits, not a useful clinical signal.
Disclaimer
This calculator is for educational use only and isn't a substitute for professional medical advice. Discuss your numbers with a clinician who can interpret them in the context of your full health picture.