How to Read a CDC Growth Chart

To read a CDC growth chart, first make sure you have the correct chart. CDC charts for children ages 2 through 19 are separated by sex and by measurement: stature-for-age, weight-for-age, or BMI-for-age. Then follow the same five steps each time:

1. Choose the correct sex-specific chart and measurement.
2. Find the child’s age on the horizontal x-axis.
3. Find the measured height, weight, or BMI on the vertical y-axis.
4. Mark the point where the age and measurement meet.
5. See which percentile curve the point falls on or between.

A printed or PDF chart usually shows only selected percentile curves. If a point falls between two curves, the chart supports an approximate range, not an exact percentile. A calculator can produce a more precise numerical estimate by using the child’s exact dates and the documented LMS implementation, but the result still depends on accurate measurements and correct inputs.

The horizontal x-axis shows age. The vertical y-axis shows the measurement used by the chart, such as standing height, weight, or BMI. The curved lines are selected percentile curves.

A percentile describes a position in the reference population. A point at the 30th percentile means the measurement equals or exceeds about 30% of the relevant reference population. It does not mean the child earned a score of 30, and it does not by itself describe health.

Each plotted point represents one measurement taken on one date. Several accurate points can show how the child’s position changes over time, but the chart does not explain why a change occurred. Measurement quality, age calculation, and the correct chart all matter.

Use the illustration below only to learn the plotting process; it is not an official CDC chart.

1. Find the child’s age on the x-axis.
2. Find the measured value on the y-axis.
3. Follow the two coordinates until they meet.
4. Compare the point with the nearest printed percentile curves.

In the illustration, the example point lies between the 25th and 50th percentile curves. The correct manual reading is “between the 25th and 50th percentiles.” The picture does not support an exact percentile such as the 37th. For a numerical estimate between printed curves, use the calculator after checking the dates, units, and measurement.

One point shows where one measurement falls in the reference population. A growth pattern requires repeated, accurate measurements over time.

Apparent movement can come from real growth, but it can also come from measurement differences. Shoes, bulky clothing, posture, an uneven floor, a different scale, incorrect dates, or mixed units can move a plotted point. Before interpreting a surprising change, check the measurement and input details.

Growth charts are not intended to be used as the sole diagnostic instrument. They contribute to an overall picture that can include growth history, development, nutrition, health history, physical examination, and professional judgment.

To calculate the arithmetic change between two dated height or weight measurements, use the Growth Velocity Calculator . That tool calculates a rate of change; it does not diagnose the cause or decide whether the rate is appropriate for a particular child.

1. Using the wrong age range. Use WHO standards before age 2 and CDC charts from age 2 onward in U.S. clinical settings.
2. Using the wrong sex-specific chart. Confirm the chart before plotting the point.
3. Plotting recumbent length as standing stature. These are different measurement methods and are not interchangeable.
4. Rounding age to the nearest whole year. Use the child’s birth date and measurement date so the age coordinate is accurate.
5. Mixing pounds with kilograms or inches with centimeters. Check the unit labels on both the chart and the measurement.
6. Treating weight-for-age as a BMI category. Weight-for-age does not adjust for height and is not a weight-status classification.
7. Reading a point between printed curves as an exact percentile. Describe the interval or use a calculator for a numerical estimate.

Accurate measurement reduces avoidable error. For standing height, remove shoes and bulky clothing, use a firm floor and flat wall, keep the child upright, and use a rigid headpiece. For weight, use a digital scale on a firm floor and remove shoes and heavy clothing.

A printed chart is useful for understanding the axes, curves, and approximate position. Use the Child Growth Chart Calculator when you want a numerical percentile estimate based on the child’s exact birth date, measurement date, and entered measurements.

The calculator uses the site’s documented CDC LMS implementation. It does not correct an inaccurate measurement, replace a clinician’s assessment, or convert a single result into a diagnosis.

Calculate height, weight, and BMI percentiles

Discuss the chart with a healthcare professional when:

• the result still differs markedly from the child’s medical record after dates, units, and measurement technique are checked;
• repeated accurate measurements show a persistent or unexpected change;
• there are related concerns about nutrition, development, illness, or other symptoms; or
• you are unsure which chart or measurement method applies.

Do not use one plotted point alone to start, stop, or change treatment.