BMI Calculator
Calculate your Body Mass Index in metric or imperial units. See where you sit on the WHO scale, with a clear category and a health disclaimer.
Runs in your browser — nothing uploaded
Measurements
Calculate your Body Mass Index — a quick screening number for adult height-and-weight in a healthy range. This tool supports both metric and imperial inputs, shows your category on the standard WHO scale, and computes the weight range that would put you in the healthy zone at your current height.
Private by design — your data never leaves your device
How to use it
No account, no upload — it all happens on your device.
1
Pick metric (cm and kg) or imperial (feet/inches and pounds) units.
2
Type your height and weight in the fields. The BMI updates as you type.
3
Read your BMI number and category, and the healthy-weight range at your height.
4
Treat the result as a starting point, not a diagnosis — see the disclaimer below the result.
BMI categories (adults, WHO)
The standard thresholds for adults 20+ years old.
| BMI | Category | What it means |
|---|---|---|
| Below 18.5 | Underweight | May indicate undernutrition or higher risk of nutritional deficiency. |
| 18.5 – 24.9 | Healthy weight | Range associated with the lowest risk on average across the adult population. |
| 25.0 – 29.9 | Overweight | Associated with modestly higher risk of cardiovascular and metabolic conditions. |
| 30.0 and above | Obese | Stronger association with cardiovascular and metabolic risk; often broken into class I (30-34.9), II (35-39.9), III (40+). |
What BMI does and doesn't tell you
- Good as a screening signal.Across large populations, BMI correlates with body fat and with several health risks. That's why doctors use it as a first check.
- Bad at individual nuance.A muscular athlete and a sedentary person can have the same BMI with very different body composition. BMI doesn't look at where fat is stored (visceral vs subcutaneous), which matters more than the headline number.
- Not for children or pregnancy. Children use age-and-sex-specific percentile charts, not adult thresholds. BMI during pregnancy is meaningful only before conception or well after birth.
- Ethnic adjustments exist. Some health bodies use lower cut-offs (23 overweight, 27.5 obese) for South Asian and East Asian populations because cardiovascular risk rises at a lower BMI in these groups.
Better-paired measurements
- Waist circumference. A waist over 94 cm (men) or 80 cm (women) is independently associated with higher metabolic risk, regardless of BMI.
- Waist-to-height ratio. Keep your waist below half your height. Simple, and a better fit-vs-fat signal than BMI alone.
- Body composition. DEXA, hydrostatic weighing, or a tape-and-skinfold estimate gives a fat-percentage number BMI cannot.
Frequently asked
What's the formula for BMI?
BMI = weight (kg) ÷ height (m)². For imperial inputs, BMI = (weight in lb × 703) ÷ (height in inches)². The two formulas give the same result — they're just unit-shuffled.
What are the standard BMI categories?
The World Health Organization classifies BMI as: under 18.5 underweight, 18.5–24.9 healthy, 25–29.9 overweight, 30 and above obese. Some countries adjust these thresholds for population-level health risk (Asian populations sometimes use 23 and 27.5).
Is my data sent anywhere?
No. BMI is one arithmetic operation that happens in your browser. Your height and weight are not uploaded, stored, or shared.