Question 1

What growth standards does this calculator use?

Accepted Answer

The calculator uses WHO Child Growth Standards (weight-for-age, length/height-for-age, weight-for-length, and head-circumference-for-age). These are the international standards recommended for children 0-5 years and adopted by most countries outside the US. The CDC recommends WHO charts for 0-2 years and CDC charts for 2-20 years in the US.

Question 2

What does a percentile mean?

Accepted Answer

A percentile shows how your child's measurement compares to other children of the same age and gender. The 50th percentile is the median. The 75th percentile means your child is larger than 75% and smaller than 25% of children the same age and gender. A wide range (roughly 3rd to 97th percentile) is considered normal.

Question 3

Is a low or high percentile bad?

Accepted Answer

Not by itself. What matters most is the trend over time. A child who stays consistently around their own percentile curve is usually growing well. Talk to your pediatrician if your child crosses percentiles sharply, is below the 3rd or above the 97th, or you have any concerns.

Question 4

Why does the calculator use Z-scores?

Accepted Answer

A Z-score (standard deviation score) shows exactly how far above or below the median a measurement is. Z-scores are more precise than percentiles at the extremes and are used by WHO and pediatricians to detect undernutrition, overweight, and stunting.

Question 5

Is my child's data private?

Accepted Answer

Yes. All calculations run entirely in your browser. No data is uploaded or stored anywhere.