Baby clothes sizes: how to choose a gift that fits

The number on the label isn't an age or a weight but the maximum body length the garment is made for. So size 62 fits a baby who measures up to about 62 cm, and it covers everything from roughly 57 cm. This comes from the European standard EN 13402, under which children's clothes are labelled by body height.

The age that shops print next to the size (say “2–4 months”) is only a conversion based on an average baby. According to the WHO growth standards, an average boy measures about 61 cm at three months and around 76 cm at one year, with girls a centimetre or two less. Any individual baby can easily be a whole size off the average, in either direction.

Two more practical points: a double size such as 62/68 means the garment lasts across both sizes (it's usually looser or has a turn-up cuff), and cotton shrinks a little after its first hot wash. The cut also varies from brand to brand — with some makers, a 68 comes up rather narrow and short.

The adorable little outfit in size 50 is the gift most likely to end up in a box with the tag still on. There are four reasons.

Babies are born right at the edge of it. The average newborn is about 50 cm long, so half of all babies are bigger from day one than size 50 is made for. And babies grow fastest in their first weeks — according to the WHO curves, they gain roughly 4 cm a month in the first two months.

Everyone gives it. A gift “for the new baby” tempts you towards the smallest size because it looks the cutest. The parents then have ten things in size 50 and only a few weeks to wear them.

The first weeks are all about comfort. A baby is changed several times a day, so at home it's bodysuits, sleepsuits and zip-up all-in-ones that win. Dresses with buttons down the back or little shirts hardly ever get a turn in the first six weeks.

The season is wrong. A thick snowsuit in size 56 for a baby born in April won't get used before winter, because by November the baby will be three sizes on.

Size 44 is made for premature babies, who are born smaller and lighter. You won't usually find it in ordinary shops, and it doesn't belong in the layette for a baby born at term — even a small newborn will probably fit into it for just a few days.

If the baby arrived early, on the other hand, this is exactly the gift the parents don't have: they weren't expecting the baby so soon, and a standard size 50 is too big. Do ask first what they need, though — hospitals often have rules about what premature babies can wear, and front fastenings and soft seams matter more than looks.

A rough layette for a baby born at term, covering the first three months. The quantities are a sensible starting point, not a rule — it depends on how often you do the washing.

Clothes are the gift most likely to miss, because you're aiming at a number that changes every month. If in doubt, stick to the rule “two sizes up from what the baby wears now”, or choose a gift that doesn't depend on size at all. Tips on sharing new-baby gifts out with others are in New baby gifts: three piles and what goes where, and for a christening, where godparents traditionally give a keepsake meant to last, see Christening gifts: who gives what and how to avoid doubling up.

If you'd like to give something the child won't outgrow in a month, it could be a personalised book in which the child, based on a photo, is the hero. For a baby it's more of a gift for later — it comes into its own once they can listen to a story, perhaps for a first birthday.