Baby sizing has its own quiet logic, and once you can see the shape of it, the whole drawer makes more sense.
For the first year, sizes are generally grouped in three-month spans. As a rough guide, newborn tends to fit babies up to around 9 pounds, 0–3 months often lands between 8 and 12 pounds, 3–6 months somewhere around 12 to 16, and 6–12 months carrying through the back half of the first year as baby grows into the high teens and low twenties in pounds. After the first birthday, the spans widen to six months — 12–18 months, then 18–24 months — before the toddler sizing of 2T begins.
The part that surprises most people is that these labels aren’t standardized. A piece marked 3 months from one maker might fit at six weeks, while the same label elsewhere won’t come into its own until well into month four. That’s not a flaw in any single brand so much as the nature of baby clothing as a whole. It’s why so many size charts lean on weight and height rather than age alone — those numbers tend to tell you more than the month printed on the tag.
If there’s a gentle takeaway, it’s this: a size chart is a guide, not a rule, and reading for your baby’s measurements rather than their age in weeks usually gets you closer. Babies also spend the most time in the 3-to-12-month range, which is often where a wardrobe earns its keep — the pieces worn through morning naps, afternoon walks, and the soft middle of an ordinary day.
Sizes will shift faster than feels possible. Somewhere in there, the chart stops being a worry and becomes a quiet record of how much has already grown.
