BMI Calculator
Enter your weight and height to find your Body Mass Index, see which category it falls in, and view your healthy weight range.
Last updated:
How it works
Enter your weight
Type your weight in kilograms.
Enter your height
Type your height in centimetres.
Read your result
Your BMI, category, and healthy range appear instantly.
How BMI is calculated
Body Mass Index divides your weight by the square of your height. Because height is measured in centimetres here, it is converted to metres first.
BMI = weight (kg) / height (m)²A person weighing 70 kg at 1.75 m has a BMI of 70 / (1.75 × 1.75) ≈ 22.9 kg/m².
Worked examples
| Scenario | Calculation | Result |
|---|---|---|
| 60 kg, 165 cm | 60 / 1.65² | 22.0 — Normal |
| 85 kg, 175 cm | 85 / 1.75² | 27.8 — Overweight |
| 50 kg, 170 cm | 50 / 1.70² | 17.3 — Underweight |
Conversion reference
| Category | BMI range (kg/m²) |
|---|---|
| Underweight | Below 18.5 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese | 30.0 and above |
Quick facts
- BMI is a screening tool, not a diagnosis.
- It does not distinguish muscle from fat.
- Athletes may read as overweight despite low body fat.
- Ranges differ for children and some ethnic groups.
- It was devised in the 1830s to describe populations, not individuals.
- Waist-to-height ratio can flag risk that BMI misses.
Dr. Jordan Avery
Registered Dietitian
- RD
- MSc Nutrition
Jordan reviews health calculators for clinical accuracy and writes about evidence-based nutrition.
Frequently asked questions
BMI is a useful population-level screen but does not account for muscle mass, bone density, or fat distribution, so it can misclassify athletes and older adults.
For most adults a BMI between 18.5 and 24.9 kg/m² is considered the healthy range.
No. The calculation runs entirely in your browser and nothing is sent to a server.
Divide your weight in kilograms by your height in metres squared. For example, 70 kg at 1.75 m is 70 / (1.75 × 1.75) ≈ 22.9 kg/m². If you use pounds and inches, multiply (pounds ÷ inches²) by 703.
The BMI formula and the adult category thresholds are the same for men and women. Body composition differs on average between sexes, which is one reason BMI is a screen rather than a diagnosis.
For adults, a BMI of 25.0–29.9 kg/m² is classed as overweight and 30.0 kg/m² or above as obese, following World Health Organization guidance.
No — for under-18s, BMI is interpreted against age-and-sex percentile charts rather than the fixed adult bands, because a healthy range changes as children grow.
Muscle is denser than fat, so very muscular people can have a high BMI while carrying little body fat. For trained bodies, body-fat percentage or waist-to-height ratio is a better signal.