BMI for children

BMI calculations are also recommended for use in children and adolescents. Our BMI calculator works for children. BMI for younger individuals is calculated in the same way as for adults. However, the same limit values for overweight and obesity do not apply. The threshold values differ depending on the child’s age and gender.

In order to get a correct assessment of BMI in children, the result should be compared with tables or percentiles. In general, children are classified as overweight and have obesity at a lower BMI than adults.

During childhood and adolescence, the relationship between weight and height varies with age. The limit values that determine a healthy BMI between the ages of up to 18 years, therefore, depend mainly on age and gender.

In an average adult, the limit for overweight is set at BMI 25. Above that number, the person is classified as overweight. At a BMI greater than 30, it is said that the person is obese. For individuals, over 18 years, the same BMI calculation applies as for an adult. However, other limits apply for children under 18 years of age. The younger the child, the lower the threshold of overweight and obesity.

Iso BMI

When calculating overweight and obesity for children, a measure called iso BMI is used. Iso BMI compares a child’s BMI value with an adult. A result of 25 or more is overweight, and over 30 is regarded as obesity. These values come from the same limits for overweight and obesity as for an average adult over 18 years.

Iso BMI is standardized and is based on scientific findings. It was developed by the International Obesity Task Force (IOTF), an international organization that fights obesity.

Calculate BMI for children

You can use our BMI calculator to determine your child’s BMI. Then compare the result with the table below. The table shows limit values for overweight and obesity, depending on the individual age and gender. BMI limits for overweight and obesity narrows at a younger age.

BMI for children
Overweight BMI Obesity BMI
Age Boy Girl Boy Girl
18 25,00 25,00 30,00 30,00
17,5 24,73 24,85 29,70 29,84
17 24,46 24,70 29,41 29,69
16,5 24,19 24,54 29,14 29,56
16 23,90 24,37 28,88 29,43
15,5 23,60 24,17 28,60 29,29
15 23,29 23,94 28,30 29,11
14,5 22,96 23,66 27,98 28,87
14 22,62 23,34 27,63 28,57
13,5 22,27 22,98 27,25 28,20
13 21,91 22,58 26,84 27,76
12,5 21,56 22,14 26,43 27,24
12 21,22 21,68 26,02 26,67
11,5 20,89 21,20 25,58 26,05
11 20,55 20,74 25,10 25,42
10,5 20,20 20,29 24,57 24,77
10 19,84 19,86 24,00 24,11
9,5 19,46 19,45 23,39 23,46
9 19,10 19,07 22,77 22,81
8,5 18,76 18,69 22,17 22,18
8 18,44 18,35 21,60 21,57
7,5 18,16 18,03 21,09 21,01
7 17,92 17,75 20,63 20,51
6,5 17,71 17,53 20,23 20,08
6 17,55 17,34 19,78 19,65
5,5 17,45 17,20 19,47 19,34
5 17,42 17,15 19,30 19,17
4,5 17,47 17,19 19,26 19,12
4 17,55 17,28 19,29 19,15

Percentile and standard deviation

The limits between BMI levels in children aged 0-5 years for the diagnosis of overweight and obesity is determined as the 97th and 99th percentiles, respectively. For those aged 6-18, being overweight is defined as a BMI above +1 SD (standard deviation) and obesity as a BMI value above +2 SD.

However, keep in mind that each child develops differently, and the BMI figures do not necessarily match with all children. When uncertain, contact knowledgeable healthcare personnel for consultation.

Click here to read about what applies to BMI for the elderly population.