BMI Calculator
Enter your height and weight and we will work out your body mass index and tell you what range counts as healthy for your height.
This calculator gives general estimates for information only. It is not medical advice and does not replace a consultation with a doctor or other qualified health professional.
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The formula
BMI = weight (kg) / height (m)². In pounds and inches: BMI = 703 x weight (lb) / height (in)².
What BMI is and what it is not
Body mass index is a quick screening number: your weight divided by your height squared. It was designed for populations, and doctors use it as a first look because it is simple, not because it is perfect.
It does not measure body fat, where the fat sits, your fitness, or your blood pressure and blood sugar. Two people with the same BMI can have very different health.
The adult categories (WHO)
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight |
| 25 to 29.9 | Overweight |
| 30 to 34.9 | Obesity class I |
| 35 to 39.9 | Obesity class II |
| 40 and above | Obesity class III |
A worked example
Someone who is 175 cm tall and weighs 70 kg: 1.75 x 1.75 = 3.0625, and 70 / 3.0625 = 22.9. That sits inside the healthy range. For that height, a healthy weight is roughly 56.7 to 76.3 kg.
What to do with the number
If you are outside the healthy range, it is worth a conversation with your doctor, who can look at waist size, blood tests and family history. If you are inside it, BMI is not a reason to change anything.
This calculator is for adults. For anyone aged 2 to 19, BMI is read against growth charts for age and sex, so use the child BMI calculator and talk to a paediatrician.
Examples to check
Type these into the calculator above to see how it behaves. Every result below was produced by the same calculator code that runs on this page.
| What you enter | What you get |
|---|---|
| Height (cm): 175; Weight (kg): 70 | BMI: 22.9 |
| Height (cm): 160; Weight (kg): 62 | BMI: 24.2 |
| Height (feet): 5; Height (inches): 9; Weight (lb): 190 | BMI: 28.1 |
| Height (cm): 182; Weight (kg): 105 | BMI: 31.7 |
BMI Calculator: frequently asked questions
Is BMI accurate for everyone?
No. BMI only compares weight with height. It cannot tell muscle from fat, so very muscular people can score as overweight, and older adults who have lost muscle can score as healthy while carrying extra fat. Use it as a starting point, not a verdict.
What is a healthy BMI range?
For adults, the WHO range for a healthy weight is 18.5 to 24.9. Some groups, including many people of South Asian descent, are advised to use lower cut-offs because health risks rise at lower BMI values.
Can I rely on this result as medical advice?
No. It is a general estimate for information only. It cannot replace a check-up, and your doctor can interpret the numbers for your own situation.
Is what I enter in this calculator saved or sent anywhere?
No. The calculation runs in your browser, so what you enter is not sent to our servers. We only count, anonymously, whether a tool ran successfully.
Is this calculator free to use?
Yes. It is free, needs no sign-up and has no usage limit.
Last reviewed: October 3, 2026