# Child Weight Percentile Calculator

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

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

## Inputs

- Sex
- Age (years, months)
- Weight (kg, lb, st, g)

## Results

- Weight-for-age z-score
- Weight percentile
- Percentile group
- Median weight for age

## Formula

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

## Explanation

Weight-for-age shows how heavy a child is compared with peers, but it does not account for height – a tall child will naturally be heavier. Use the BMI percentile calculator to judge weight relative to height.

### How to use the Child Weight Percentile Calculator

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

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

### How it works

Enter sex, age and weight.

### 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, g

### Example values

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

Age (years)Weight percentile (%)4100692852109123e-1166e-11
*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: 26 kg.

Results — Weight-for-age z-score = 0.06; **Weight percentile = 52 %**; Percentile group = 50th–85th; Median weight for age = 25.8 kg.

## Key terms

- **Weight-for-age**: Weight compared with children of the same age and sex.

## FAQ

**What weight percentile is normal?**
Between about the 3rd and 97th, especially if it matches the height percentile.

**Why use BMI percentile instead?**
BMI accounts for height, which weight-for-age does not.

**How often should children be weighed?**
At routine checks; frequent weighing at home is not needed.


## Sources

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