How baby sizes work
The European size is their height
In Europe, a baby clothing size is simply the height in centimetres. A size 68 is made for a baby up to 68 cm tall; once they pass that, it's time for 74. Sizes go up in steps of six centimetres: 50, 56, 62, 68, 74, 80, 86, 92 and 98.
That's why the most reliable way to get it right isn't age, it's measuring. Lay your baby on their back, gently straighten one leg and measure from the top of the head to the heel. With that number, the chart above gives you the size with nothing to interpret.
What about the months on the label?
The months on many labels (3-6 months, 6-9 months) translate that height into the age of an average baby. They help when you're buying for a baby who isn't in front of you, but they're an approximation: two four-month-olds can be a whole size apart.
Babies grow about 25 cm in their first year, and nearly half of that in the first four months. So the first sizes last weeks and the last ones half a year. Size 56 can be outgrown in a month; size 86 usually lasts from 12 to 18 months.
Why a 68 isn't the same in every brand
The size says which height the garment is made for, not how big the garment is. Each brand decides the cut: some run roomy, some snug; some leave room for the nappy and some don't. Nordic brands tend to run large, with cuffs you can fold back; some fashion chains run smaller.
The system changes too. The United States and the United Kingdom size by age (0-3M, 3-6M, 12M) and often by weight, and an American 3-6M usually matches a European 68, but not always. Fabric matters as well: cotton shrinks a little in the first washes, and a snug ribbed bodysuit doesn't behave like a knitted sweater.
If your baby wears cloth nappies, allow half a size more in bodysuits and trousers.
What size to buy for a baby of X months
If you can't measure them, age is a good clue. A two-month-old usually wears size 62; at four months, 68; at six they're still in 68 but about to move to 74; at nine, 74; at a year, 80; and at 18 months, 86. Girls tend to run a little behind boys, especially after the first birthday.
What matters most isn't the size they wear today, it's when the garment will be worn. If you're buying for three months from now, work out the size for then: in the first year, three months is a whole size. And if on that date they'll be a couple of centimetres from the change, take the next one. The calculator above does that sum for you.
What size to give a newborn
For a newborn, give size 56 or 62, not 50. Size 50 is outgrown in days, and many babies never wear it at all. Size 56 will last the first month and 62 until three months, which is when changes of clothes are really needed.
The rule works at any age: for a gift, go one size up from what they wear. It will fit for months instead of weeks, and if it arrives a little big, they'll grow into it. Think about the season too: a coat in the next size up only helps if the cold comes while it fits.
Tips for buying the next size up
If they're between two sizes, pick the bigger one. A rolled-up sleeve lasts two more months; a sleeve that's too short can't be fixed.
Think about the season, not just the size. Before buying that coat in the sales, work out the size they'll wear when the cold comes back: a baby in size 68 in June will be in size 80 by December.
Don't stock up on the first sizes. Sizes 50 and 56 are worn for a very short time and they're exactly what people give most. A few basics will do; keep the budget for size 68 onwards, which lasts longer.
And above all: use it. Lovely clothes saved "for a special day" are the first to be outgrown with the tags still on. Once you know how long each garment will fit, it's easy to wear it in time.