How much should a 21-month-old baby weigh?
In short
- These numbers come from the US CDC 2000 growth reference, a reference based on US children -- not the World Health Organization's growth standards. For babies under 2, CDC and the American Academy of Pediatrics recommend doctors use the WHO growth standards instead, whatever the feeding type; in India, the Indian Academy of Pediatrics recommends WHO's charts for children under five. Ask your doctor which chart they use for your baby.
- In the CDC 2000 reference, the middle 94% of 21-month-old boys weigh between 10.07 and 15.13 kg, and girls, between 9.65 and 14.41 kg.
- Babies grow at very different paces. These numbers are a range most babies fall in, not a target -- your doctor tracks the trend over several visits, not any single measurement.
- This page also shows the CDC 2000 reference's typical length and head circumference for a 21-month-old baby, below.
Which growth chart does your doctor use?
The CDC 2000 reference used on these pages is a licence-clean data source, not the reference doctors are told to use for infants. For ages 0-2, CDC/AAP recommend clinicians use the WHO growth standards instead, and (for India) IAP recommends WHO's charts under age five. Every growth page must say so plainly, near the top, and never imply the CDC 2000 numbers are 'the' standard a doctor uses to judge a baby under 2.
CDC and the American Academy of Pediatrics (AAP) recommend that U.S. health care providers in primary-care settings use: WHO child growth standards for children birth to 2 years to monitor growth, regardless of feeding type.
CDC / American Academy of Pediatrics (AAP), Recommendations and Rationale -- Growth Chart Training -- CDC. Retrieved 2026-09-26. Quoted verbatim.
Indian academy of pediatrics (IAP) produced and recommended IAP 2015 Growth charts for monitoring Indian children between the age of 5 to 18 years and recommended simplified WHO growth charts for monitoring of children under the age of five years.
Indian Academy of Pediatrics (IAP), Pediatrician-friendly growth charts for 0-18-year-old Indian children (Dr Bakul Parekh, Dr Vaman Khadilkar), iapindia.org. Retrieved 2026-09-26. Quoted verbatim.
How much should a 21-month-old baby weigh?
In the CDC 2000 reference, the middle 94% of 21-month-old boys weigh between 10.07 and 15.13 kg, and girls, between 9.65 and 14.41 kg.
| Percentile | Boys | Girls | Source |
|---|---|---|---|
| 3th | 10.07 kg (10073 g) | 9.65 kg (9649 g) | CDC |
| 5th | 10.33 kg (10325 g) | 9.87 kg (9867 g) | CDC |
| 10th | 10.73 kg (10728 g) | 10.22 kg (10219 g) | CDC |
| 25th | 11.44 kg (11442 g) | 10.85 kg (10854 g) | CDC |
| 50th | 12.3 kg (12302 g) | 11.64 kg (11640 g) | CDC |
| 75th | 13.24 kg (13238 g) | 12.52 kg (12524 g) | CDC |
| 90th | 14.15 kg (14152 g) | 13.42 kg (13418 g) | CDC |
| 95th | 14.73 kg (14734 g) | 14 kg (14005 g) | CDC |
| 97th | 15.13 kg (15128 g) | 14.41 kg (14409 g) | CDC |
How long should a 21-month-old baby be?
In the CDC 2000 reference, the middle 94% of 21-month-old boys measure between 78.8 and 91.6 cm, and girls, between 77.2 and 89.9 cm.
| Percentile | Boys | Girls | Source |
|---|---|---|---|
| 3th | 78.8 cm | 77.2 cm | CDC |
| 5th | 79.6 cm | 78 cm | CDC |
| 10th | 80.8 cm | 79.2 cm | CDC |
| 25th | 82.9 cm | 81.3 cm | CDC |
| 50th | 85.1 cm | 83.6 cm | CDC |
| 75th | 87.4 cm | 85.9 cm | CDC |
| 90th | 89.5 cm | 87.9 cm | CDC |
| 95th | 90.8 cm | 89.1 cm | CDC |
| 97th | 91.6 cm | 89.9 cm | CDC |
What's a typical head circumference for a 21-month-old baby?
In the CDC 2000 reference, the middle 94% of 21-month-old boys have a head circumference of between 45.7 and 50.9 cm, and girls, between 44.5 and 49.7 cm.
| Percentile | Boys | Girls | Source |
|---|---|---|---|
| 3th | 45.7 cm | 44.5 cm | CDC |
| 5th | 46.1 cm | 44.8 cm | CDC |
| 10th | 46.6 cm | 45.4 cm | CDC |
| 25th | 47.4 cm | 46.2 cm | CDC |
| 50th | 48.3 cm | 47.1 cm | CDC |
| 75th | 49.3 cm | 48 cm | CDC |
| 90th | 50.1 cm | 48.9 cm | CDC |
| 95th | 50.6 cm | 49.3 cm | CDC |
| 97th | 50.9 cm | 49.7 cm | CDC |
Source
CDC 2000 Growth Charts for the United States, National Center for Health Statistics. See the data files. Retrieved 2026-09-26. Public domain -- see how we source and check every page.
Plot your own baby's measurements against these curves in our growth chart tool.
Babies grow at very different paces. These numbers are a range most babies fall in, not a target -- your doctor tracks the trend over several visits, not any single measurement.
Educational summary of CDC data, not medical advice.