Size chart
Primary baby size chart
Primary publishes 11 baby and toddler sizes, Newborn to 4, by weight and height. Checked against size-chart-server.primary.codes on October 4, 2026.
Size chart
- Newborn5.1 to 9 lb
- 0-3M9 to 11.9 lb
- 3-6M11.9 to 15 lb
- 6-9M15 to 18.1 lb
- 6-12M15 to 22 lb
- 9-12M18.1 to 22 lb
- 12-18M22 to 26.9 lb
- 18-24M26.9 to 30 lb
- 230 to 33.1 lb
- 333.1 to 35.9 lb
- 435.9 to 39.9 lb
Weight in lb, exactly as Primary publishes it.
Does Primary run small or large?
True to sizeAcross 11 size labels that other brands also use, Primary's published ranges sit close to the middle of the pack. The same label covers about the same baby.
Based on published size charts compared with other brands. This is not a fit review.
What a typical baby wears in Primary
For a baby in the middle of the WHO growth chart, with room to grow. Your baby's own measurements give a closer answer in the calculator below.
| Age | Typical weight | Typical length | Primary size |
|---|---|---|---|
| Birth | 7.3 lb | 19.5 in | 0-3M |
| 3 months | 13.5 lb | 23.9 in | 3-6M |
| 6 months | 16.8 lb | 26.2 in | 6-12M |
| 9 months | 18.9 lb | 28 in | 9-12M |
| 12 months | 20.5 lb | 29.5 in | 12-18M |
| 18 months | 23.3 lb | 32.1 in | 18-24M |
| 2 years | 26.1 lb | 34 in | 2 |
| 3 years | 31.1 lb | 37.6 in | 3 |
The chart as published
The original wording from Primary's chart, size by size.
| Size | Weight | Height or length | Age |
|---|---|---|---|
| NB | 5-9 lb | up to 18 in | Not published |
| 0-3 | 9-12 lb | 18-23 in | Not published |
| 3-6 | 12-15 lb | 23-25 in | Not published |
| 6-9 | 15-18 lb | 25-27 in | Not published |
| 6-12 | 15-22 lb | 25-29 in | Not published |
| 9-12 | 18-22 lb | 27-29 in | Not published |
| 12-18 | 22-27 lb | 29-31 in | Not published |
| 18-24 | 27-30 lb | 31-33 in | Not published |
| 2 | 30-33 lb | 33-35 in | Not published |
| 3 | 33-36 lb | 35-38 in | Not published |
| 4 | 36-40 lb | 38-41 in | Not published |
Notes on this chart. The brand shows its chart on product pages. Labels are printed without units (0-3, 2, 3). Metric values are the brand's own. 6-12 overlaps 6-9 and 9-12 as published. NB through 3 come from the baby chart and 4 from the kids chart.
Sources
- Brand's own site: https://size-chart-server.primary.codes/all-baby-clothing
- Brand's own site: https://size-chart-server.primary.codes/metric:all-baby-clothing
- Brand's own site: https://size-chart-server.primary.codes/all-kids-clothing
- Brand's own site: https://size-chart-server.primary.codes/metric:all-kids-clothing
Retrieved October 4, 2026. Brands update their charts, so check the brand's page before a big purchase. This site is not affiliated with Primary.
Calculator
What Primary size on your date?
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