BMI Calculator for Children and Teenagers

Check a child’s BMI by age and percentile in seconds

Use this BMI Calculator for Children and Teenagers to estimate BMI for children and teens and see how it compares with others of the same age and sex. Children’s BMI is interpreted differently from adults, so age and sex are essential for a meaningful result.

kg / cm lb / ft + in

Weight (kg):

Height (cm):

Sex:

Date of birth:

WHO (default) IOTF (Cole)

BMI result (children 2–18 years)

*Results are for informational purposes only. If you are worried about your child’s health, weight, or growth, speak to a GP or paediatrician.

BMI calculator for adults

How the BMI Calculator for Children and Teenagers Works

1. Enter details

Enter the child’s age, sex, height, and weight, as these are needed for an accurate calculation.

2. Choose a standard

Select whether you want results based on WHO or IOTF, then click calculate.

3. View and save

Check the BMI result and explanation, then download the result as a PDF to keep for later.

Why use this calculator

No data storage

Your entries are not saved, so your information stays private.

Fast results

Your result appears immediately once all fields are completed.

Easy to use

The form is simple and works well for quick checks at home.

BMI for children explained: WHO vs IOTF

For calculating a child’s Body Mass Index, the WHO and IOTF standards are most commonly used.

WHO (World Health Organization)

WHO uses growth charts and percentiles to show how a child’s BMI compares with children of the same age and sex.

Results are often grouped like this: underweight below the 5th percentile, healthy weight from the 5th to 85th, overweight from the 85th to 95th, and obesity above the 95th percentile.

IOTF (International Obesity Task Force)

IOTF uses age and sex specific cut-offs that link child BMI to adult thresholds.

In simple terms, it maps child results to the adult BMI 25 line for overweight and the adult BMI 30 line for obesity, adjusted by age and sex.

Body Mass Index Calculator for Children and Teenagers

Healthy weight table by age

A healthy weight table can support the calculator by showing typical weight ranges from ages 2 to 18 based on WHO style growth data, split by age and sex and paired with typical height. Use it as a guide only, as children grow at different rates and small differences are common.

Imperial (lb, ft in)

Metric (kg, cm)

Age	Boys (lb)	Girls (lb)	Typical height boys/girls (ft in)
2	24-31	22–29	2:09-2:11 / 2:09-2:11
3	29-35	26–33	3:00-3:03 / 2:12-3:03
4	31-40	29–37	3:03-3:06 / 3:03-3:06
5	35-44	33–42	3:05-3:09 / 3:05-3:08
6	40-51	37–49	3:08-4:00 / 3:07-3:11
7	44-57	42–55	3:10-4:02 / 3:10-4:02
8	49-66	46–64	4:00-4:04 / 4:00-4:04
9	53-75	51–73	4:02-4:06 / 4:02-4:06
10	57-88	55–84	4:04-4:08 / 4:04-4:08
11	66-99	62–97	4:06-4:11 / 4:06-4:10
12	75–110	71–110	4:08-5:01 / 4:09-5:01
13	84-121	79–121	4:11-5:03 / 4:11-5:03
14	93-137	88–132	5:01-5:06 / 5:01-5:05
15	104-150	97–141	5:03-5:08 / 5:03-5:07
16	115-163	104–150	5:05-5:10 / 5:03-5:07
17	123-172	110–154	5:07-5:10 / 5:03-5:07
18	132-181	115–159	5:07-5:11 / 5:04-5:08

Age	Boys (kg)	Girls (kg)	Typical height boys/girls (cm)
2	11–14	10–13	84–90 / 83–89
3	13–16	12–15	92–99 / 91–98
4	14–18	13–17	99–107 / 98–106
5	16–20	15–19	105–114 / 104–113
6	18–23	17–22	111–121 / 110–120
7	20–26	19–25	117–127 / 116–126
8	22–30	21–29	123–133 / 122–132
9	24–34	23–33	128–138 / 127–137
10	26–40	25–38	133–143 / 132–142
11	30–45	28–44	138–149 / 138–148
12	34–50	32–50	143–154 / 144–154
13	38–55	36–55	149–160 / 150–160
14	42–62	40–60	155–167 / 156–166
15	47–68	44–64	161–173 / 159–169
16	52–74	47–68	166–177 / 160–170
17	56–78	50–70	169–179 / 161–171
18	60–82	52–72	171–181 / 162–172

The data in this table is for informational purposes and is based on average values under WHO standards. Children grow at different rates, and small differences are completely normal.

If you are concerned about a child’s weight, height, or development, be sure to speak with a paediatrician or another healthcare professional.

Rising obesity

According to WHO data, more than 39 million children under the age of 5 are overweight.

Environmental impact

A sedentary lifestyle and more time spent in front of screens can significantly contribute to weight gain.

Global undernutrition

Around 45 million children under the age of 5 suffer from severe undernutrition (acute undernutrition).

Frequently asked questions

What is a BMI Calculator for Children and Teenagers?

A BMI Calculator for Children and Teenagers estimates BMI using a child’s height and weight, then interprets it using age and sex. Unlike adult BMI, the result is usually shown as a percentile or age-based category.

Why is child BMI different from adult BMI?

Children’s bodies change as they grow, so the same BMI value can mean different things at different ages. That is why child BMI is compared to growth references for the same age and sex.

What does a BMI percentile mean?

A percentile shows how a child’s BMI compares with others of the same age and sex. For example, the 60th percentile means the BMI is higher than about 60 percent of peers.

Should I worry if my child’s BMI is above the healthy range?

A single result is not enough to diagnose a problem, but it can be a useful prompt to look at overall growth trends. If the BMI stays high over time or you have concerns, speak with a GP or paediatrician.

How often should I check my child’s BMI?

Checking occasionally can be helpful, but frequent checks can cause unnecessary worry. Many parents review it every few months or during routine health checks, especially during growth spurts.

Can this calculator diagnose underweight, overweight, or obesity?

No, it provides an estimate based on standard references and is for informational use only. A healthcare professional will consider growth patterns, medical history, and other measurements before making any assessment.