Height Percentile
50%
Weight
50%
Age
12 mo
Growth Percentiles
50%
Height Percentile
Weight Pct
50%
Height Z
0
Inputs
Result
At 12 months, the WHO median for boys is 75.7 cm height and 9.6 kg weight. Z = ((75.7/75.7)^1 - 1) / (1 × 0.0323) = 0. The 50th percentile means exactly average.
Inputs
Result
WHO median for 6-month girls: 65.7 cm. Z = ((67/65.7)^1 - 1) / (1 × 0.0345) = 0.574. Percentile ≈ 71.7%. This girl is slightly above average in both height and weight.
Growth percentiles use the WHO/CDC LMS method: Z = ((measurement/M)^L - 1) / (L × S), where L, M, and S are age- and sex-specific parameters. The Z-score converts to a percentile showing what percentage of children are smaller. The 50th percentile is the median.
| Z-Score | Percentile | Interpretation | Action |
|---|---|---|---|
| Below -2 | <3rd | Below normal range | Medical evaluation recommended |
| -2 to -1 | 3rd-16th | Low-normal | Monitor trend |
| -1 to +1 | 16th-84th | Normal range | No concern |
| +1 to +2 | 84th-97th | High-normal | Monitor trend |
| Above +2 | >97th | Above normal range | Medical evaluation recommended |
WHO charts (0-2 years) describe how children should grow under optimal conditions with breastfeeding. CDC charts (2-20 years) describe how US children actually grew. AAP recommends WHO charts for 0-2 and CDC charts for 2-20.
The 50th percentile means your child is at the exact midpoint: 50% of children the same age and sex are taller/heavier, and 50% are shorter/lighter. Being at the 50th percentile is average, but any percentile from 5th to 95th is generally considered normal.
Concern is warranted when a child drops or gains 2+ percentile lines (e.g., from 75th to 25th), falls below the 3rd or above the 97th percentile, or has a BMI-for-age above the 95th percentile. A single measurement is less meaningful than the trend over time.
| Percentile | Height | Weight | Action |
|---|---|---|---|
| <3rd | Short stature evaluation | Failure to thrive screen | Refer to specialist |
| 3rd-5th | Monitor closely | Nutrition review | Follow-up in 3 months |
| 5th-95th | Normal variation | Normal variation | Routine monitoring |
| >95th | Tall stature evaluation | Obesity screening | Lifestyle counseling |
Pediatricians measure growth at every well-child visit: monthly for the first 6 months, every 3 months from 6-24 months, and annually after age 2. More frequent measurements at home can be unreliable due to measurement technique variations.
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Last Updated: Mar 25, 2026
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