BMI – What Does it Mean?

The most common method used to see if your child is overweight or obese is through calculating their Body Mass Index (BMI).

BMI= weight (kg)/ height^2 (m2). (i.e. weight (kg) divided by height (m), then divide the answer by height again)

A child’s height and body weight is constantly fluctuating and therefore, does not follow the standard adult overweight and obese BMI values. According to the age, the corresponding values for overweight (adult BMI= 25) and obese (adult BMI= 30) for children are shown in Table 1.

Table 1: Classification of overweight and obesity for children and adolescents

Age (years) BMI equivalent to overweight BMI equivalent to obese
Males Females Males Females
2 18.41 18.02 20.09 19.81
2.5 18.13 17.76 19.80 19.55
3 17.89 17.56 19.57 19.36
3.5 17.69 17.40 19.39 19.23
4 17.55 17.28 19.29 19.15
4.5 17.47 17.19 19.26 19.12
5 17.42 17.15 19.30 19.17
5.5 17.45 17.20 19.47 19.34
6 17.55 17.34 19.78 19.65
6.5 17.71 17.53 20.23 20.08
7 17.92 17.75 20.63 20.51
7.5 18.16 18.03 21.09 21.01
8 18.44 18.35 21.60 21.57
8.5 18.76 18.69 22.17 22.18
9 19.10 19.07 22.77 22.81
9.5 19.46 19.45 23.39 23.46
10 19.84 19.86 24.00 24.11
10.5 20.20 20.29 24.57 24.77
11 20.55 20.74 25.10 25.42
11.5 20.89 21.20 25.58 26.05
12 21.22 21.68 26.02 26.67
12.5 21.56 22.14 26.43 27.24
13 21.91 22.58 26.84 27.76
13.5 22.27 22.98 27.25 28.20
14 22.62 23.34 27.63 28.57
14.5 22.96 23.66 27.98 28.87
15 23.29 23.94 28.30 29.11
15.5 23.60 24.17 28.60 29.29
16 23.90 24.37 28.88 29.43
16.5 24.19 24.54 29.14 29.56
17 24.46 24.70 29.41 26.69
17.5 24.73 24.85 29.70 29.84
18 25.00 25.00 30.00 30.00

Article author: Grace Kim, Nutritionist, Bachelor of Health Sciences, U.Q – Published November 2017.