European Children's Clothing Sizes Explained: A Parent's Guide to EU, UK, and US Labels

If you have ever held up two garments in the same nominal size and found one comfortably roomy and the other unwearable, you have run into the central problem of children's clothing sizing: there is no single system. There are at least three, they measure different things, and brands apply them inconsistently on top of that.

For families in Luxembourg, this comes up constantly. A wardrobe here might hold French, Danish, British, German, and American labels at the same time — and each one describes size in its own dialect. This guide is the translation.

 

The One Thing Worth Knowing First

European sizes describe the child's height in centimetres. British and American sizes describe the child's age.

That distinction explains most of the confusion. A European size 86 means the garment is cut for a child who is roughly 86 cm tall. It says nothing about whether that child is fourteen months old or twenty-two months old — and both are perfectly normal at that height.

Age-based sizing works backwards from an average. "18 months" means the garment is cut for the height an average eighteen-month-old happens to be. If your child sits above or below that average — and most children do, in one direction or the other — the label becomes a rough guess rather than a measurement.

This is why we recommend the same first step to every parent: measure your child's height, and write it down. With that one number, European sizing becomes straightforward and age-based sizing becomes translatable. Without it, you are guessing in both systems.

 

How to Measure

Stand your child against a wall without shoes, heels together, back flat. Mark the wall at the top of the head with a flat object held level, then measure from the floor to the mark. Re-measure roughly every three months during the first three years, and every six months after that — growth in early childhood arrives in bursts rather than steadily.

For younger babies who cannot stand, lay them flat on a firm surface and measure from crown to heel with the legs gently extended.

The Conversion Table

Read this table as a starting point rather than a rule. The height column is the reliable one; the age columns are averages that many perfectly healthy children sit outside of.

The French Complication

French brands frequently label by age in months and years rather than centimetres — and French ages tend to describe the upper limit of the range rather than the middle of it.

A French garment marked "18 mois" is generally cut to fit a child up to eighteen months, not a child who has just turned eighteen months. The practical consequence is that French labels often run a size smaller than parents expect, which is the single most common sizing surprise families report when buying French children's brands for the first time.

This is not a manufacturing inconsistency — it is a different convention, applied consistently. Once you know it, it stops catching you out.

We cover how this plays out brand by brand, including which labels run small and which are cut more generously, in our guide to which children's brands run small.

 

American Sizing Runs Its Own Course

American children's labels are typically cut more generously than European ones at the same nominal age, particularly through the chest and shoulders. The gap widens as sizes go up — the difference is modest at twelve months and noticeable by age six.

A useful rule of thumb: if you are moving from a French or Danish wardrobe to an American brand, expect the same nominal age to feel roomier. Moving in the other direction, expect it to feel tighter.

Two labelling quirks worth knowing:

• "T" sizes (2T, 3T, 4T) are American toddler sizes, cut with room for a nappy and a toddler's proportions. They are not interchangeable with plain 2, 3, 4, which are cut for older, leaner children.
• The "M" suffix on American labels means months (18M = 18 months), while a plain number usually means years.

 

British Sizing Sits in Between

UK children's sizing uses age like the American system but tends to be cut closer to European proportions, particularly on brands with a long European retail presence. In practice, British labels are the least likely to surprise you in either direction — but the same rule applies: check the height equivalent on the brand's own chart when one is available.

How Sizes Appear on Blueberry

Because our catalogue spans French, Danish, German, British, and American labels, we list sizes in the form the garment itself carries, and add the height equivalent wherever the original label provides one.

That gives you two common formats across the shop:

• Dual format — for example 18M / 81. The first figure is the age as the brand labelled it; the second is the height in centimetres the garment is cut for. When you see this format, the centimetre figure is the one to trust.
• Age-only format — for example 12-18M or 5Y. Used where the brand labels by age alone and provides no height equivalent. For these, use the conversion table above alongside your child's measured height.

We do not silently convert sizes between systems on the listing. A garment labelled 86 is listed as 86, because the label is the piece of information that stays true regardless of which chart anyone consults.

 

When the Numbers Still Do Not Settle It

Height gets you most of the way, but children are not uniform, and a few situations call for judgement rather than a chart:

Long torso, short legs, or the reverse. Height alone cannot capture proportion. If trousers consistently fit in length but gape at the waist, or sleeves come up short while the body fits, size to the measurement that matters for the garment type — length for trousers and sleeves, chest and shoulders for tops and outerwear.

Outerwear. Coats need room for layers underneath. Sizing outerwear to exact height leaves no space for a jumper, which is exactly what a coat is for. Size up.

Anything with a fixed waistband. Non-adjustable trousers and skirts are the first thing a child outgrows and the least forgiving when the fit is wrong. If you are between sizes here, take the larger one.

Knitwear and jersey. Both have some give and tolerate a slightly generous fit well. Woven cotton, denim, and tailored pieces do not — they fit or they do not.

Buying the Size Ahead

One quiet advantage of shopping pre-loved: you are not tied to the retail calendar. A shop selling new stock carries the current season in the current sizes, so buying a size ahead often means waiting for it to appear. A curated pre-loved catalogue carries whatever has come in, which means next year's size is frequently sitting there today.

That makes it practical to buy ahead when you find the right piece rather than when the calendar allows it — particularly for outerwear and occasion pieces, which are worn few times and often arrive with plenty of life left.

For the signs that a child is genuinely ready to move up a size — and what to do with the wardrobe they have just left behind — see our guide on when to size up on children's wear.

Frequently Asked Questions

Do EU sizes correspond exactly to my child's height? They correspond to the height the garment is cut for, which is the closest thing to a universal standard in children's clothing. Cut and fit still vary between brands, so treat the centimetre figure as a strong starting point rather than a guarantee.

My child is between two sizes. Which do I choose? Generally the larger one, particularly for outerwear, fixed-waistband trousers, and anything you want to last more than a season. The exception is occasion wear that needs to fit properly on a specific date.

Why does the same nominal size fit differently across brands? Because each brand applies the system to its own block and its own proportions. French labels tend to run closer to the body, American labels more generously. Our brand fit guide covers the labels we handle most often.

Do pre-loved garments fit the same as new ones? Broadly yes, though cotton and jersey can settle slightly with repeated washing. Every piece we list is inspected and graded before it goes on the site, and any shape or fit issue is described on the product page. Our clothing conditions page explains how each grade is defined.

How often should I re-measure? Every three months up to age three, then every six months. Growth in early childhood comes in bursts, and a measurement from six months ago is often a size out of date.

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Shop by Size, Not by Guesswork

Every listing on Blueberry carries the size as the brand labelled it, with the height equivalent where the original label provides one — so you can match against your child's measurement rather than a chart's average. Browse the full collection or explore the labels we curate on Brands We Love.

And when they have grown out of the size they are in, our Sellback programme turns that wardrobe into cash or store credit toward the next one.

Shop pre-loved →