https://www.gosh.nhs.uk/conditions-and-treatments/general-health-advice-children/eat-smart/obesity-lowdown/your-bmi/
Your BMI
The Body Mass Index or BMI is the easiest way of finding out if you are a healthy weight. You weigh yourself, then your measure your height. Then you use the BMI calculation below.
weight (kilograms)
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height x height (metres)
Once you have the calculation, look at the table below and plot accordingly to your age and sex.
| OVERWEIGHT | OBESE | |||
| Age (years) | Boys | Girls | Boys | Girls |
| 5 | 17.4 | 17.1 | 19.3 | 19.2 |
| 5.5 | 17.5 | 17.2 | 19.5 | 19.3 |
| 6 | 17.6 | 17.3 | 19.8 | 19.7 |
| 6.5 | 17.7 | 17.5 | 20.2 | 20.1 |
| 7 | 17.9 | 17.8 | 20.6 | 20.5 |
| 7.5 | 18.2 | 18.0 | 21.1 | 21.0 |
| 8 | 18.4 | 18.3 | 21.6 | 21.6 |
| 8.5 | 18.8 | 18.7 | 22.2 | 22.2 |
| 9 | 19.1 | 19.1 | 22.8 | 22.8 |
| 9.5 | 19.5 | 19.5 | 23.4 | 23.5 |
| 10 | 19.8 | 19.9 | 24.0 | 24.1 |
| 10.5 | 20.2 | 20.3 | 24.6 | 24.8 |
| 11 | 20.6 | 20.7 | 25.1 | 25.4 |
| 11.5 | 20.9 | 21.2 | 25.6 | 26.1 |
| 12 | 21.2 | 21.7 | 26.0 | 26.7 |
Adapted from: Cole et al, 2000. British Medical Journal.