CALCULATORS & CONVERTERS
BMI Calculator — Body Mass Index (Metric & Imperial)
Calculate your BMI from height and weight in metric or imperial units and see the WHO category. Runs in your browser, private, no signup.
ملفاتك لا تغادر جهازك أبدًا.
22.9 BMI
Normal weight
Calculate your Body Mass Index from your height and weight in metric (kg and cm) or imperial (pounds and feet/inches) units, and see which standard category it falls into. BMI is a quick screening number that relates weight to height.
The formula is exact: BMI = weight in kilograms ÷ height in metres squared (kg/m²). The imperial form is (pounds ÷ inches²) × 703, which is the same formula with the unit factors folded in. For example, 70 kg at 1.75 m is 70 ÷ (1.75 × 1.75) = 22.9.
What BMI does not tell you
BMI uses only height and weight, so it cannot distinguish muscle from fat or show where fat sits on the body. A muscular athlete can land in the 'overweight' range despite low body fat, while someone with little muscle can have a 'normal' BMI yet carry high body fat.
It also does not account for age, sex, or ethnicity, and the same number can carry different health implications across populations. Treat BMI as a rough screening signal, not a diagnosis — measures like waist circumference or a body-composition assessment give a fuller picture, and any real decision about your health belongs with a qualified clinician who knows your full situation.
WHO adult BMI categories
| BMI (kg/m²) | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obese (class I) |
| 35.0 – 39.9 | Obese (class II) |
| 40.0 and above | Obese (class III) |
These thresholds are for adults. Children and teenagers are assessed on age- and sex-specific percentile charts, not these fixed cut-offs.
Frequently asked questions
- What is the BMI formula?
- Weight in kilograms divided by height in metres squared: BMI = kg / m². The imperial version, (pounds / inches²) × 703, gives the same number.
- Is BMI accurate for athletes?
- Often not. Muscle is dense and heavy, so very muscular people are frequently mislabelled as overweight by BMI even at low body fat. For them, body-composition or waist measures are more informative.
- Should I make health decisions based on this number?
- Not on its own. BMI is a starting point for a conversation, not a verdict. Use it alongside other measurements and professional medical advice.
- Is my height and weight kept private?
- Yes. The calculation runs entirely in your browser and nothing is sent anywhere, so your figures stay on your device.