Baby Knitting & Crochet Size Chart
Baby sizing grows faster, and less predictably, than any other age band on this site — a difference of just a few weeks can shift a real infant meaningfully across these bands, which is exactly why this chart is built around measurement ranges rather than a single number per age.
The chart
| Size label | Age equivalent | Chest | Head circumference | Foot length |
|---|---|---|---|---|
| Preemie | Preemie | 12–14 in | 11–12.5 in | 2.5–3 in |
| Newborn | 0–3 months | 16–18 in | 13–14.5 in | 3–3.75 in |
| 6 months | 3–6 months | 17–19 in | 16–17 in | 3.75–4.25 in |
| 12 months | 6–12 months | 18–20 in | 17.5–18.5 in | 4.25–4.75 in |
These bands follow the same standard body-measurement convention this site's adult sizing and toddler & child chart use, scaled to the infant range.
Why "age equivalent" is the least reliable column
Chest, head, and foot measurements all correlate with age only loosely in this window — a baby genuinely can sit meaningfully above or below their age-typical band without anything being unusual about their growth. If you can measure the actual infant, do that and match against the numbered columns directly; use the age-equivalent column only as a fallback for an unknown recipient, and treat it as the least trustworthy number on this whole chart.
Which measurement matters for which project
A hat needs head circumference. A sweater or bodysuit needs chest. Socks need foot length — though, as the sock project-size pages note, foot circumference has no equivalent standard chart at all and needs to be measured directly regardless of which age band the length falls into.
Why growth-room decisions matter more here than at any other age
Because babies at this stage outgrow a size within weeks rather than a full season, many patterns and crafters deliberately size up by one band, trading a temporarily loose fit for a longer useful window before the piece is outgrown. This trade-off is discussed in more depth on the baby sweater project page, where sizing-for-growth is weighed directly against sizing-for-current-fit.
Fastenings and finishing matter as much as the measurement
At this size especially, how easy a piece is to get on and off — snap placement, a wide-enough neck opening, secure but simple fastenings — affects how much a finished piece actually gets worn, sometimes more than a precise chest match does. Choosing a fastening a tired parent can manage one-handed is a genuinely practical design consideration, not an afterthought.
FAQ
Is this chart based on a single manufacturer's or designer's convention? It follows the general body-measurement convention used broadly across the pattern industry (the same source underlying this site's adult and child charts), not one single brand's proprietary sizing.
How much does a specific baby's measurement typically vary from these bands? Real variation is common and normal — these bands describe a typical range, not a guarantee, and measuring an actual baby directly always beats an age-based estimate when it's possible to do so.
Where do I turn a measurement from this chart into an actual stitch count? The Cast-On Calculator converts any target circumference or width from this chart into a correctly rounded stitch count for your own gauge and chosen stitch pattern.