Cat & Jack Baby Size Chart — Fit by Weight & Height
The Cat & Jack baby-clothing size chart, size by size — the weight and height each label covers, and how Cat & Jack compares with the Size Index median for each size (taken across the distinct brand charts that print a weight for it). Based on the brand’s own published chart (retrieved 2026-09-02); we compare published charts and do not handle or test any garment.
Across its published chart, each Cat & Jack size covers about 0.9 lb less than the Size Index median, averaged across 12 sizes in our Size Index. If your baby is near the top of a weight range, size up in Cat & Jack.
Cat & Jack baby size chart (weight & height)
| Size | Fits weight | Height | Size Index median | Cat & Jack vs median |
|---|---|---|---|---|
| Preemie | up to 5.5 lb | up to 17.5 in | 5.5 lb | 0 |
| Newborn | 6–8 lb | 18–20 in | 8 lb | 0 |
| 0-3M | 9–12 lb | 20.5–23.5 in | 12 lb | 0 |
| 3-6M | 12.5–16 lb | 24–25.5 in | 17 lb | −1 lb |
| 6-9M | 16.5–19.5 lb | 26–27.5 in | 20 lb | −0.5 lb |
| 12M | 20–23 lb | 28–30.5 in | 23.5 lb | −0.5 lb |
| 18M | 23.5–26 lb | 31–32.5 in | 27 lb | −1 lb |
| 24M | 26.5–28 lb | 33–35.5 in | 30 lb | −2 lb |
| 2T | 26.5–28 lb | 33–35.5 in | 30.5 lb | −2.5 lb |
| 3T | 28.5–32 lb | 36–38.5 in | 34 lb | −2 lb |
| 4T/4 | 32.5–37 lb | 39–43 in | 38 lb | −1 lb |
| 5T/4 | 37.5–42 lb | 43.5–44.5 in | 42 lb | 0 |
Read the “vs median” column to see where Cat & Jack differs: a positive number means that size covers heavier babies than the typical brand (runs bigger on paper); negative means smaller. Compared across all 12 sizes, as in our Size Index; the 4T/4 and 5T/4 rows are compared with the 4T and 5T medians.
How we built this
There is no US standard for baby-clothing sizes, so the same label fits different weights at different brands. This page reproduces the Cat & Jack published size chart and compares each size to the Size Index median for that size, taken across 13 to 27 distinct brand charts depending on the size, from our 30-brand Baby Clothing Size Index 2026. Figures are from the brand’s published chart (retrieved 2026-09-02); we compare published charts only and never claim to have measured or tested a garment. For clothing fit only — not a guide to how much a baby should weigh.