What This BMI Calculator Tells You
Enter your height and weight to instantly see your Body Mass Index (BMI) — a number that shows whether your current weight falls into the underweight, normal, overweight, or obese range for your height. You also get the healthy weight range for your exact height, so you know what the target looks like.
Everything runs in your browser. No data is sent anywhere — your numbers stay completely private.
How to Use the BMI Calculator
- Enter your height in centimetres (for example, 172 cm).
- Enter your weight in kilograms (for example, 68 kg).
- Hit Calculate. Your BMI score appears instantly, along with your category and the healthy weight range for your height.
- Use the result as a starting point for a conversation with your doctor or dietitian — not as a diagnosis.
Worked Example
Say you are 165 cm tall and weigh 72 kg. Here is what happens:
- Height in metres: 1.65 m
- Height squared: 1.65 × 1.65 = 2.7225
- BMI: 72 ÷ 2.7225 = 26.5
- Category: Overweight (25–29.9 range)
- Healthy weight range for 165 cm: roughly 50.4 – 68.1 kg
That one number — 26.5 — immediately tells you where you sit relative to the standard ranges, and the healthy range shows exactly how close or far the target is.
How BMI Is Calculated
The formula is straightforward. Divide your weight in kilograms by your height in metres, squared:
BMI = weight (kg) ÷ height (m)²Nothing else goes into it — no age, no sex, no fitness level. That simplicity is both its strength (quick and free) and its biggest limitation (more on that below).
WHO BMI Categories
The World Health Organization (WHO) defines four standard categories based on the BMI score:
| Category | BMI Range |
|---|---|
| Underweight | Below 18.5 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese (Class I) | 30.0 – 34.9 |
| Obese (Class II) | 35.0 – 39.9 |
| Obese (Class III) | 40.0 and above |
A BMI in the 18.5–24.9 range is generally considered a healthy weight for most adults. The worked example above (165 cm, 72 kg → BMI 26.5) lands in the overweight band.
How to Read Your Result — and Its Limits
BMI is a screening measure, not a health diagnosis. It is a useful first signal, but it has real blind spots:
- Muscle vs fat: A muscular athlete can have a high BMI yet carry very little body fat. BMI treats all weight the same.
- Where fat is stored: Two people with the same BMI can have very different health risks depending on whether fat sits around the abdomen or elsewhere. Waist circumference is a useful companion measure.
- Age and sex: Older adults and women tend to carry more body fat at the same BMI than younger adults and men. The standard ranges do not adjust for this.
- Ethnicity: Research suggests some ethnic groups — including South Asian, East Asian, and Middle Eastern populations — face higher health risks at lower BMI scores than the WHO thresholds imply.
The CDC recommends using BMI alongside other measures — such as waist circumference, blood pressure, and cholesterol — for a fuller picture of health.
This calculator is for educational purposes only and is not medical advice. Please talk to your doctor or a registered dietitian before making any health decisions based on your result.
Practical Tips for a Healthy Weight
Whatever your number shows, small consistent changes tend to work better than drastic ones. A few evidence-backed habits worth building:
- Eat mostly whole foods. Vegetables, legumes, whole grains, lean proteins, and fruit cover most of your nutritional needs without heavy calorie counting.
- Watch portion sizes, not just food types. Even healthy foods add up. Smaller plates and eating slowly both help.
- Move for at least 150 minutes a week. WHO guidelines recommend moderate aerobic activity (like brisk walking) as a baseline for adults.
- Prioritise sleep. Poor sleep disrupts the hormones that control hunger and fullness, making it harder to maintain a healthy weight.
- Cut back on ultra-processed foods and sugary drinks — these are the biggest drivers of excess calorie intake for most people.
- Seek support if you need it. A dietitian can build a plan around your real life, not a generic chart.
Reaching or staying in a healthy weight range is not about a single number. It is about habits you can actually keep.
Your Privacy
This BMI calculator runs entirely in your browser. Your height and weight are never uploaded, stored, or shared. Once you close the tab, nothing is saved anywhere.
Ready to check your number? Use the calculator at the top of this page — it takes about ten seconds.