For most gifting situations, 3–6M or 6–9M is the right call. Newborn and 0–3M sizes are outgrown in weeks (often before the gift is even unwrapped), and parents tend to receive a surplus of them. Sizes 3–6M and 6–9M offer a longer wear window and land at an age when parents are more likely to dress babies in intentional outfits.

If you know the baby's due date or birth month, account for the season: a September baby will be in 6–9M clothing through winter, so a cozy or layerable piece in that size is especially thoughtful.

It varies by baby, but as a general guide: Newborn fits 0–4 weeks; 0–3M fits roughly 4–8 weeks; 3–6M fits about 6–8 weeks; 6–9M fits 8–10 weeks; 9–12M fits 8–10 weeks; 12–18M fits 3–4 months; and 18–24M fits 3–4 months.

Larger sizes have a much longer wear window, which is one reason they make better gifts. A 90th-percentile baby may skip 0–3M entirely.

No, they are different sizes. NB (Newborn) is designed for babies up to about 8 lbs and 21.5 inches, which typically means the first few weeks of life. 0–3M is the next size up, fitting babies roughly 8–12 lbs and 21–24 inches.

A baby born at average weight (7–8 lbs) will often skip NB entirely or wear it for only a week or two. 0–3M is the more common starting size for most full-term newborns.

Most Ashmi & Co. pieces run true to size. Knit items have a slight natural stretch that makes them forgiving of in-between sizing.

The one exception: the Chase Sweatshirt Jogger Set runs large. Customers have reported buying 6–9M for a 12-month-old and having it fit perfectly. Always check the individual product page for brand-specific sizing notes.

For NB and 0–3M, aim for 5–7 bodysuits, 4–5 pants or rompers, and 2–3 dressier pieces. For 3–6M through 9–12M, you can keep a leaner rotation: 6–8 bodysuits, 4–6 pants or rompers, and 2–4 occasion pieces.

By 12–18M and beyond, babies stay in each size longer, so a slightly larger wardrobe makes sense. Between gifts and hand-me-downs, most parents end up with more than enough of the smaller sizes and wish they had more in 9–12M and up.