How the calculator works
- Growth rate. The height gained between the two measurements is divided by the time between them to give a yearly rate in inches and centimeters.
- Percentiles.Your child's age at each measurement is worked out from the date of birth, and each height is placed on the CDC stature-for-age chart using the official LMS data, the chart US pediatricians use from age 2. The calculator counts how many of the chart's major lines (5th, 10th, 25th, 50th, 75th, 90th, 95th) your child crossed.
- Comparisons. The rate is compared with typical growth for age (AAFP), with how much the median child on the CDC chart grows between the same two ages, and with the growth your child would need to stay exactly on the same percentile.
- Flags. It points out growth under 5 cm (2 in) a year before puberty, a fall across two or more major percentile lines, a height below the 3rd percentile, and measurements less than 6 months apart, which make yearly rates unreliable.
For accurate numbers, measure without shoes against a flat wall on a hard floor, lower a book flat onto the top of the head, and record to the nearest ⅛ inch or 0.1 cm (CDC). For the full picture by age, see how much kids grow per year.
Normal growth rate by age
Typical height gain per year. These are typical values, not cutoffs: what matters most is that a child keeps growing along their own percentile.
| Age | Typical growth per year |
|---|---|
| 2 to 3 years | About 8 cm (3 in) |
| 3 to 5 years | About 6–7 cm (2.4–2.8 in) |
| 5 years to puberty | 5–6 cm (2–2.4 in) |
| Just before puberty (low point) | 5–5.5 cm (2–2.2 in) |
| Puberty peak, girls (around 11½) | 8–12 cm (3–5 in) |
| Puberty peak, boys (around 13½) | 10–14 cm (4–6 in) |
Source: AAFP 2008 and AAFP 2015 (growth velocity by age); peak ages from MedlinePlus.
How much the CDC median grows each year
The change in the CDC median (50th percentile) height from one birthday to the next. In the puberty years, individual children grow more than this in their peak year: the CDC charts average many children whose growth spurts come at different ages, which flattens the spurt.
| Age (years) | Boys | Girls |
|---|---|---|
| 2 → 3 | 8.5 cm (3.3 in) | 8.9 cm (3.5 in) |
| 3 → 4 | 7.3 cm (2.9 in) | 6.8 cm (2.7 in) |
| 4 → 5 | 6.7 cm (2.6 in) | 6.9 cm (2.7 in) |
| 5 → 6 | 6.5 cm (2.6 in) | 7.1 cm (2.8 in) |
| 6 → 7 | 6.4 cm (2.5 in) | 6.8 cm (2.7 in) |
| 7 → 8 | 6.1 cm (2.4 in) | 6.1 cm (2.4 in) |
| 8 → 9 | 5.6 cm (2.2 in) | 5.3 cm (2.1 in) |
| 9 → 10 | 5.1 cm (2.0 in) | 5.1 cm (2.0 in) |
| 10 → 11 | 4.9 cm (1.9 in) | 6.0 cm (2.4 in) |
| 11 → 12 | 5.5 cm (2.2 in) | 7.2 cm (2.8 in) |
| 12 → 13 | 7.0 cm (2.8 in) | 6.0 cm (2.3 in) |
| 13 → 14 | 7.8 cm (3.1 in) | 3.2 cm (1.3 in) |
| 14 → 15 | 6.1 cm (2.4 in) | 1.5 cm (0.6 in) |
| 15 → 16 | 3.6 cm (1.4 in) | 0.7 cm (0.3 in) |
| 16 → 17 | 1.8 cm (0.7 in) | 0.4 cm (0.1 in) |
| 17 → 18 | 0.9 cm (0.3 in) | 0.2 cm (0.1 in) |
Source: computed from the official CDC 2000 stature-for-age LMS data.
Frequently Asked Questions
How much should my child grow in a year?▾
It depends on age. Typical figures are about 8 cm (3 in) from age 2 to 3, about 6–7 cm (2.4–2.8 in) a year from 3 to 5, and 5–6 cm (2–2.4 in) a year from 5 until puberty, with a low point of about 5–5.5 cm just before puberty starts. At the puberty growth spurt, girls grow about 8–12 cm (3–5 in) a year at the peak and boys about 10–14 cm (4–6 in).
How far apart should the two height measurements be?▾
Ideally 6 to 12 months, and at least 3 to 6 months. Children grow in spurts and tend to grow faster in spring and summer, and turning a short gap into a yearly rate multiplies any measuring error: a 0.5 cm slip over 3 months becomes a 2 cm-a-year error. Measure the same way each time, at about the same time of day.
What growth rate is too slow?▾
Before puberty, children normally grow at least about 5 cm (2 in) a year, and a slower rate is a common reason for referral to a specialist. A height that falls across two major percentile lines after age 2, or a height below the 3rd percentile, is also a reason to talk to your pediatrician. Re-measure first, since small errors are common at home.
Why did my child's percentile change during puberty?▾
Puberty timing varies by several years, and the CDC charts average children whose growth spurts come at different ages. A child who starts puberty early often moves up the chart for a while, and a late bloomer often drifts down and catches up later. Signs of puberty before 8 in girls or 9 in boys, or none by 13 in girls or 14 in boys, are worth a visit.
Can I use this calculator for a baby or toddler under 2?▾
No. Children under 2 are measured lying down and plotted on the WHO growth standards, and lying-down length runs about 0.7–0.8 cm longer than standing height, so mixing the two would make growth look slower than it is. Use the baby height growth velocity calculator for children under 2, and this one once both measurements are standing heights after the second birthday.
Sources
- AAFP: Diagnostic Approach to Short and Tall Stature (2008), normal growth velocity by life stage
- AAFP: Evaluation of Short and Tall Stature in Children (2015), growth velocity by age and referral criteria
- CDC Growth Charts (2000), stature-for-age 2–20 years
- CDC: Use of WHO and CDC Growth Charts in the US (MMWR 2010)
- CDC: Measuring Children's Height and Weight
- MedlinePlus: Adolescent development (growth spurt timing)
- AAP (HealthyChildren.org): Physical Development in Girls, What to Expect
- MedlinePlus: Delayed puberty in boys
- Kaplowitz & Bloch 2016, AAP clinical report: Evaluation and Referral of Children With Signs of Early Puberty