Baby clothes sizes are labelled by age, but babies rarely read the label — weight is the better guide. Use this simple chart to buy the right sizes (and the right amounts) without ending up with a drawer full of outfits your baby never wears.
Baby clothes size chart
| Size | Age (approx.) | Weight (approx.) |
|---|---|---|
| Newborn (NB) | 0–1 month | Up to 3.5 kg |
| 0–3 months | 1–3 months | 3.5–6 kg |
| 3–6 months | 3–6 months | 6–8 kg |
| 6–12 months | 6–12 months | 8–10 kg |
| 12–18 months | 12–18 months | 10–11 kg |
Sizes vary a little between brands — when in doubt, go by weight and size up rather than down.
How many of each to buy
Newborns grow out of the smallest sizes fast, so buy sparingly at the bottom and more in 0–3 months. A rough starter set:
- 6–8 onesies / bodysuits (a few NB, more 0–3m)
- 4–6 sleepsuits / rompers
- 2–3 pairs of mittens and 2 soft hats
- 4–6 pairs of socks or booties
- 1–2 going-out outfits + a light jacket
👕 Shop soft, safe baby clothing
Browse our newborn and 0–3 month range — gentle fabrics, easy snaps, delivered islandwide with cash on delivery.
Shop baby clothing →Fabric & comfort tips (for Sri Lanka's climate)
- Choose breathable cotton — it's kind to newborn skin in the heat
- Look for envelope necks and front snaps for easy changes
- Avoid rough seams, tight elastic and scratchy tags
- Wash everything before first use in a gentle detergent
Baby clothes sizing — FAQs
What size should I buy for a newborn?
Newborn size fits most babies up to ~3.5 kg for the first weeks, then 0–3 months. Buy a few NB pieces and more 0–3m.
How many onesies does a newborn need?
About 6–8 across Newborn and 0–3 month sizes — babies change often.
Should I size up?
Yes — sizing up slightly is safer. Babies grow fast, and roomier clothes last longer.