Size Guide
Every little one grows at their own pace — and every brand cuts a little differently. Use this guide as your starting point, and when in doubt, we always say size up. A slightly roomier babygrow is always better than one your baby has grown out of before you've had a chance to snap a photo.
Baby Size Chart
| Age Size | Height | Weight |
|---|---|---|
| Newborn | Up to 56 cm / 22 in | Up to 4.5 kg / 10 lb |
| 0–3 months | 56–62 cm / 22–24 in | 4.5–5.8 kg / 10–13 lb |
| 3–6 months | 62–68 cm / 24–27 in | 5.8–7.5 kg / 13–16 lb |
| 6–9 months | 68–74 cm / 27–29 in | 7.5–9 kg / 16–20 lb |
| 9–12 months | 74–80 cm / 29–31 in | 9–10 kg / 20–22 lb |
| 12–18 months | 80–86 cm / 31–34 in | 10–11.5 kg / 22–25 lb |
| 18–24 months | 86–92 cm / 34–36 in | 11.5–13 kg / 25–29 lb |
| 24–36 months | 92–98 cm / 36–39 in | 13–15 kg / 29–33 lb |
These are general guidelines — fit varies between brands and styles. If your baby is between sizes or on the bigger side for their age, we'd always recommend going up a size.
How to Measure
Height
Lay your baby flat or stand them against a wall (shoes off) and measure from the top of their head to their heels. This is the most useful measurement for getting the right fit.
Weight
Use your most recent health visitor or GP weight. For newborns especially, weight is often a more reliable guide than age alone.
Not sure?
If your baby is between sizes or you're buying ahead, always size up. Babies grow into things surprisingly quickly — and a little extra room never hurts.
A note on Spanish sizing ☽
Some of our pieces are made by traditional Spanish brands, which typically run smaller than standard UK sizing. Where this applies, you'll find a Spanish fit note directly on that product's page — with clear guidance on which UK size to order.
This doesn't apply to every Spanish-style piece we stock, and sizing can vary even between Spanish brands, so please always check the individual product page first. If you're ever unsure about a specific item, just drop Holly an email at holly@milkmoon.co.uk — she knows her stock inside out and is always happy to point you in the right direction.