Weight-for-Age Percentile Calculator (WHO, 0-5 Years)

How Weight-for-Age Percentiles Work (0-5 Years)

This calculator uses the WHO Child Growth Standards to assess weight-for-age from birth through 5 years (60 months). The WHO standards are based on the Multicentre Growth Reference Study, which followed healthy breastfed children from six countries to establish how children should grow under optimal conditions.

The calculator uses the LMS method (Lambda-Mu-Sigma), a statistical technique that summarizes the distribution of weight at each age using three parameters. Lambda (L) accounts for the skewness of the distribution, Mu (M) is the median, and Sigma (S) is the coefficient of variation.

Understanding Percentiles

A percentile indicates the percentage of children who weigh less than your child. For example, if your child is at the 75th percentile, 75% of children of the same age and sex weigh less.

• 3rd to 97th percentile is considered the normal range
• Below the 3rd percentile may indicate underweight
• Above the 97th percentile may indicate overweight
• The trend over time matters more than a single measurement

Example Calculation

A 3-year-old boy (36 months) weighing 14.3 kg would be approximately at the 50th percentile (Z-score near 0), since the WHO median weight for boys at 36 months is 14.3429 kg.

Frequently Asked Questions

What age range does this calculator cover?

This calculator uses WHO growth standards for children from birth to 5 years (60 months). For infants under 24 months, you may also use our 0-24 month weight-for-age calculator for more specific analysis.

Should I use my child’s weight in kg or pounds?

You can use either unit. The calculator converts pounds to kilograms automatically. For the most accurate result, use the weight recorded at your pediatrician’s office.

How is this different from the 0-24 month calculator?

Both use WHO growth standards and the same LMS data for the 0-24 month overlap period. This calculator extends the range to 60 months (5 years), making it suitable for toddlers and preschoolers.

Are these the same charts my doctor uses?

The WHO growth standards used here are recommended by major health organizations worldwide. In the United States, the CDC recommends WHO standards for children under 2 and CDC growth charts for ages 2-20. This calculator provides the WHO standard for the full 0-5 year range.