Old Navy Baby Size Chart — Fit by Weight & Height
The Old Navy baby-clothing size chart, size by size — the weight and height each label covers, and how Old Navy compares with the median of the 30 brands in our Size Index. 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 Old Navy size covers about 1.5 lb less than the 30-brand median. If your baby is near the top of a weight range, size up in Old Navy.
Old Navy baby size chart (weight & height)
| Size | Fits weight | Height | 30-brand median | Old Navy vs median |
|---|---|---|---|---|
| Up to 7 lbs | up to 7 lb | up to 21.5 in | — | — |
| 0-3 M | 7–14 lb | 21.5–24 in | 12 lb | +2 lb |
| 3-6 M | 14–17 lb | 24–26.5 in | 17 lb | 0 |
| 6-9 M | 17–19 lb | 26.5–29 in | 20 lb | −1 lb |
| 6-12 M | 17–21 lb | 26.5–29 in | 22 lb | −1 lb |
| 12-18 M | 21–24 lb | 29–31.5 in | 27 lb | −3 lb |
| 18-24 M | 24–26 lb | 31.5–33.75 in | 30 lb | −4 lb |
| 2T | 26–28 lb | 33.75–36 in | 31 lb | −3 lb |
| 3T | 28–32 lb | 36–39 in | 34 lb | −2 lb |
| 4T | 32–36 lb | 39–42 in | 38 lb | −2 lb |
| 5T | 36–41 lb | 42–45 in | 42 lb | −1 lb |
Read the “vs median” column to see where Old Navy differs: a positive number means that size covers heavier babies than the typical brand (runs bigger on paper); negative means smaller. Compared across 10 matching sizes; our Size Index also counts the “Up to 7 lbs” row as a Newborn size, so its Old Navy average covers 11 sizes (the same −1.5 lb).
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 Old Navy published size chart and compares each size to the median of 30 brands from our 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.