Which Children's Brands Run Small? A Fit Guide to Five Labels We Love

Every parent has done this. You order the size your child wears, it arrives, and it fits like it was made for a different child entirely. Too tight across the chest. Sleeves stopping short of the wrist. Or the opposite: a jumper that could double as a nightdress.

The label was not lying to you. It was just answering a different question than you thought you were asking.

This is one of the most useful things to understand about premium European children's wear, and it becomes more useful still when you are shopping pre-loved and cannot try anything on. So here is how five of the brands we stock most deeply actually fit, and the single convention that explains almost all of the confusion.

 

The "Up To" Problem: Why French Sizing Feels So Small

French and European sizing is built on height. A garment labelled "3 ans" is cut to fit a child up to three years old, which in practice means up to roughly 94 to 96 cm. It is the ceiling of that size, not the middle of it.

American sizing works from the opposite direction. A "3T" is built for a child who is three, with a little growing room designed in. Wider through the chest, longer in the body, more relaxed everywhere.

Same number on the tag. Two entirely different promises.

So when parents say French brands run small, what is really happening is that a French 3 is closer to an American 2T. Neither label is wrong. They are simply measuring from different ends of the year, and nobody explains this at the point of purchase.

Once you know this, the rest of the guide will make immediate sense.

 

1. Petit Bateau — Runs Smallest

Of everything we stock, Petit Bateau is the label most likely to catch a parent out. It is widely considered the smallest-cut of the major European children's brands.

Two things drive it. First, the classic ribbed cotton jersey has very little give across the width, so a piece that looks generous held flat fits close on the body. Second, the fit is deliberately snug rather than roomy, which is part of what makes their bodysuits and vests layer so beautifully under everything else.

Practical guidance: size up, and for babies on the sturdier side, consider sizing up twice on bodysuits and vests. If your child comfortably wears a high-street 4, expect to be reaching for a Petit Bateau 5. Do not be put off by how small a piece looks flat, particularly in ribbed cotton, but do go up.

Where it matters most: bodysuits, vests, tees, and anything ribbed. Outerwear and knitwear are more forgiving.

2. Jacadi — Runs Small and Slim

Jacadi sizes strictly by height, and the cut is elegant and slim through the body. It is a tailored silhouette rather than a relaxed one, which is exactly what makes it look so polished, and exactly why it fits closer than parents expect.

The telling detail is in Jacadi's own guidance. Their size chart advises that if a child's measurements fall between two sizes, always take the larger one. When a brand tells you that, it is telling you something about its cut.

Practical guidance: size up roughly one year against your child's actual age, and more if your child is tall or broad. A Jacadi 3A is cut for a child up to around 96 cm, which many three-year-olds have already passed.

Where it matters most: fitted dresses, blouses, and trousers. Cardigans and coats are cut with a little more ease.

 

3. Catimini — Runs Small, and Length Goes First

Catimini follows the same French convention, with one pattern worth knowing: for most children, it is the length that becomes limiting before the width does. Parents regularly report a piece still fitting comfortably across the body while the sleeves and hem have already given up.

The practical rule parents settle on is to read a Catimini age label as an upper bound rather than a match. A Catimini 3 behaves like a 2 to 3, not like a garment for a child who has just turned three.

Practical guidance: size up one, and size up confidently if your child is tall for their age even if they are slim. Height is the constraint here, not build.

Where it matters most: dresses, tops, and anything with a defined hemline.

 

4. Sergent Major — The Most Predictable of the French Labels

Sergent Major uses the same height-based European system as the others, but with the fuller, more forgiving cut you would expect from an everyday French high-street label rather than a couture-leaning one. It is designed for nursery floors and playgrounds, and the pattern reflects that.

The result is the brand that behaves closest to its label for a child of average build. That makes it a genuinely useful anchor point: if you know how Sergent Major fits your child, you have a reliable baseline to judge the others against.

Practical guidance: true to size for most children, with the usual European caveat that the label still describes an upper bound. Size up if your child is tall or sits near the top of a size.

Where it matters most: everyday knits, tees, and joggers, where the fuller cut is most noticeable.

5. Polo Ralph Lauren — Runs Generous

Polo Ralph Lauren is the outlier in our catalogue, and the one brand where the usual advice reverses.

It uses American sizing, which is broader and boxier through the chest and shoulders, with more length in the body and sleeve. A Ralph Lauren 2T will typically fit a child noticeably longer than a Jacadi 2A, and the difference only widens as sizes go up.

Practical guidance: take your child's actual age size, or size down if your child is slim. This is the one label in this guide where sizing up can leave you with a piece that swims for a full season.

Where it matters most: polos, oxford shirts, and rugby shirts, where the boxier cut is most obvious. Knitwear runs generous throughout.

 

The Quick Reference

Three Rules That Work Across Every Brand

Judge by height, not by age. European sizing is height-based at its foundation, so a recent height measurement is worth more than a birthday. Two minutes with a tape measure against a doorframe will save you more misjudged purchases than anything else in this guide.

Anchor to a brand you already know. If a brand's 3 fit your child well, its 4 will behave predictably too. Fit consistency within a label is the single most reliable shortcut in pre-loved shopping, and it is why building a wardrobe around two or three brands you trust works so well.

When in doubt, size up. A slightly roomy piece becomes a perfect piece in a few weeks. A slightly small piece is a loss on the day it arrives. Children grow into clothes far more gracefully than they squeeze into them.

Why This Is Easier With Pre-Loved

Two quiet advantages worth naming.

The first is that these pieces have already been washed, often many times. Whatever shrinkage a garment was going to do has largely happened, so what you see is what you get. Premium European cotton is built to hold its shape through that, which is a large part of why these brands survive a second and third child at all.

The second is timing. On the high street, the next size up only exists in the current season's range, so buying ahead is a gamble against the calendar. Our catalogue is built from clothes children have already grown through, which means every size is available year-round. If this guide has convinced you that your child needs the next size in Petit Bateau rather than the one on the tag, that size is here in August as readily as it is in February.

Every piece we list carries dual EU and age sizing for exactly this reason, alongside a clearly stated condition grade so nothing about a garment is a surprise on arrival.

Frequently Asked Questions

Do all French brands run small? As a general rule, yes, though the degree varies. The underlying cause is the height-based "up to" convention rather than any one brand's pattern-cutting. Petit Bateau sits at the smallest end, Sergent Major at the most generous end, with Jacadi and Catimini in between.

What does "3A" mean on a French label? It stands for 3 ans, or three years, and corresponds to roughly 94 to 96 cm in height. Read it as the ceiling of the size rather than the middle.

My child is between sizes. Which way should I go? Up, in almost every case. The single exception in this guide is Polo Ralph Lauren, where the generous American cut usually means the smaller of the two sizes is the better fit.

Does pre-loved clothing shrink further? Rarely in any meaningful way. Most shrinkage happens in a garment's first few washes, which have already taken place before a piece reaches us. Quality European cottons are specifically constructed to hold their shape over a long life.

How do I stop guessing altogether? Measure your child's height, shop the brands whose fit you already know, and check the size details listed on each product page. Between those three habits, guesswork mostly disappears.

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Ready to shop the right size? Browse Jacadi, Petit Bateau, Catimini, Sergent Major, and Polo Ralph Lauren — or explore every label in Brands We Love.

And when the current size is outgrown, our sellback programme turns that pile into credit toward the next one.