Height & Weight Percentile Calculator for Kids (2-20)

Find your child's height-for-age and weight-for-age percentiles from the CDC 2000 Growth Charts, for boys and girls aged 2 to 20, in inches and pounds or centimeters and kilograms.

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Results will appear here once you enter your values.

How the percentile is calculated

The CDC 2000 Growth Charts describe how height (stature) and weight are distributed among US children at every age from 2 to 20. Instead of publishing every percentile, the CDC publishes three numbers for each sex and each half month of age: L (a skewness term), M (the median) and S (the spread). This calculator uses those official LMS values.

Step 1, find the reference at the exact age. The CDC rows are listed at 24, 24.5, 25.5, 26.5 months and so on. For an 8-year-old (96 months), the calculator blends the 95.5 and 96.5 month rows in proportion to the age, so a child a few weeks older gets a slightly taller median.

Step 2, convert the measurement to a z-score. z = ((X / M)^L − 1) / (L × S), where X is the height in centimeters or the weight in kilograms. A z-score of 0 means exactly the median; −1.64 and +1.64 mark the 5th and 95th percentiles.

Step 3, turn z into a percentile with the standard normal distribution. A girl who is 127 cm tall at 8 years 0 months has a z-score just under 0, which is about the 46th percentile: roughly 46 of every 100 girls her age in the reference population are shorter. Inches and pounds are converted to metric first, so both unit systems give identical answers.

What the numbers mean for your child

A percentile is a comparison, not a grade. The 25th percentile is not "worse" than the 75th; it only says where a child sits relative to the reference group. Healthy children grow along every part of the chart, and body size runs strongly in families.

  • Between the 5th and 95th percentile: where about 90% of children fall.
  • Below the 5th or above the 95th: still often normal, but it is the range where pediatricians usually look more closely, together with parents' heights and the child's growth history.
  • Crossing lines: a child who moves from the 60th to the 20th percentile for height over a year or two can matter more than a single low or high value.

The results table also shows the actual 5th, 50th and 95th percentile heights and weights at your child's age, so you can see the typical range in inches, pounds, centimeters or kilograms rather than only a rank.

For weight relative to height, the CDC recommends BMI-for-age rather than weight-for-age for children 2 and older, because weight-for-age does not account for how tall a child is.

Common measuring mistakes

  • Measuring with shoes or a hair accessory. Height should be taken standing barefoot against a wall with heels, buttocks and shoulders touching it and a flat object resting on the head.
  • Using the wrong chart for the age. These CDC charts start at 2 years. For babies and toddlers under 2, the CDC recommends the WHO growth standards, which use length measured lying down.
  • Rounding the age to whole years. Children grow several centimeters in a year, so 8 years 11 months and 8 years 0 months have noticeably different medians. Enter the extra months.
  • Comparing home and clinic weights. Clothing, a full stomach or a different scale can shift weight by a pound or more. Track the trend on the same scale.
  • Reading one measurement as a diagnosis. Growth concerns are judged from repeated measurements, family history and an exam, so share any worries with your pediatrician.

Frequently Asked Questions

Common questions about the Height & Weight Percentile Calculator for Kids (2-20)

Any percentile can be normal. About 90% of children are between the 5th and 95th percentiles on the CDC charts. Pediatricians pay more attention to values outside that range and to children who cross several percentile lines over time.

Sources & References

CDC Growth Charts: Percentile Data Files with LMS Values

Source of the stature-for-age and weight-for-age LMS parameters (statage.csv, wtage.csv) used for every percentile, and the z-score formula.
→Source: Centers for Disease Control and Prevention (CDC)

2000 CDC Growth Charts for the United States: Methods and Development (Kuczmarski RJ et al., Vital Health Stat 11, 2002)

Describes how the CDC 2000 charts and their LMS smoothing were built, and the 2-20 year age range they cover.
→Source: National Center for Health Statistics (PubMed)

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