# BMI Percentile Calculator for Children and Teens

URL: https://speedycalculator.com/calculators/health/bmi-percentile-child/
Last updated: 2026-10-30

> The BMI percentile calculator compares a child's or teenager's BMI with the CDC growth charts for their age and sex (2–20 years) and gives the percentile, z-score and weight status.

## Inputs

- Sex
- Age (years, months)
- Weight (kg, lb, st, g)
- Height (cm, in, m, ft, mm)

## Results

- BMI
- BMI-for-age z-score
- BMI percentile
- Weight status
- BMI as % of the 95th percentile

## Formula

```
BMI = weight ÷ height²
z = ((BMI ÷ M)^L − 1) ÷ (L × S), with CDC LMS values for age and sex
Percentile = Φ(z) × 100
```

## Explanation

In children, BMI is interpreted as a percentile because body fat changes with age and differs between boys and girls. Below the 5th percentile is underweight, 85th–95th overweight and the 95th or above obesity.

### How to use the BMI Percentile Calculator for Children and Teens

- **Sex**
- **Age**
- **Weight**
- **Height**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter sex, age, weight and height.

### Tips

- Measure lying length for babies under 2 and standing height from age 2.
- Use the exact age in months for babies – a few weeks matters.
- Follow the trend across several visits; crossing two major percentile lines is more important than one value.
- Discuss concerns with your paediatrician.

### Common mistakes to avoid

- Comparing a baby with the wrong sex chart.
- Reading the 50th percentile as "normal" and everything else as abnormal.
- Using corrected age incorrectly for premature babies.

### Inputs explained

FieldWhat to enterSexChoose one: Male, FemaleAgeUnits: years, monthsWeightUnits: kg, lb, st, gHeightUnits: cm, in, m, ft, mm

### What each result means

- **BMI** = [Weight]÷([Height]÷100)^2
- **BMI percentile** = ncdf([BMI-for-age z-score])×100

### Example values

How the main result changes when **Age** changes and everything else stays at the example values above:

Age (years)BMI percentile (%)48868687510581237165
*Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.*

## Worked example

Inputs — Sex: Male; Age: 8 years; Weight: 28 kg; Height: 128 cm.

Results — BMI = 17.1; BMI-for-age z-score = 0.69; **BMI percentile = 75 %**; Weight status = Healthy weight; BMI as % of the 95th percentile = 85 %.

## Key terms

- **Percentile**: Share of children of the same age and sex with a lower value.

## FAQ

**What BMI percentile is healthy for a child?**
Between the 5th and 85th percentile.

**What is severe obesity in children?**
A BMI at or above 120% of the 95th percentile.

**Which charts are used?**
The CDC 2000 BMI-for-age growth charts for ages 2–20.


## Sources

- [CDC – Clinical growth charts and LMS data files](https://www.cdc.gov/growthcharts/cdc-growth-charts.htm)