Quick answer
Buy a winter coat one size up — enough for a growth spurt and a layer underneath, but not two sizes, which lets cold air in at the neck and cuffs. Choose synthetic insulation for wet Dutch winters and down for dry cold, and let the layers underneath do most of the warmth work. And never buckle a child into a car seat wearing a bulky coat.
A winter coat is the single most expensive thing most parents buy for a child each year, and the one most likely to be outgrown before it's worn out. It's also the garment where the wrong choice is most obvious: a coat that's too big gapes, a coat that's too small gets refused at the door, and a coat that traps sweat leaves a child colder than no coat at all.
Here's how we think about it — fit first, insulation second, and the layers underneath doing more work than the coat itself.
Size up once — not twice
The instinct to buy big is a good one. Kids grow fast, coats are expensive, and a coat that lasts two winters is a coat that halves its own cost per wear. But there's a ceiling on how far that logic stretches.
Outerwear guidance is fairly consistent on this: one size up gives room for a growth spurt and for a jumper underneath. Two sizes up is generally too much for anything other than a very lightweight shell. A coat that's significantly oversized gaps at the neck and wrists — exactly the points where a well-fitted coat seals warmth in. Sleeves that hang past the fingers make mittens impossible to keep on, and a hem that reaches the knees restricts climbing and running.
Rather than guessing from age labels, measure. Take your child's chest and height, compare them to the specific brand's chart, and allow a couple of extra centimetres for the layers that go underneath. Age labels vary enormously between brands and countries; measurements don't.
This is a different question from everyday fit. Our own oversized cuts are designed with deliberate growing room built into the pattern — a coat, by contrast, has to seal at four specific points (neck, wrists, hem, hood) to do its job, which is why the maths is stricter.
Down or synthetic? It depends on how wet your winter is
Insulation works by trapping air. Both down and synthetic fills do this well — they just fail differently.
Down has the better warmth-to-weight ratio, which means a lighter, less bulky coat for the same warmth. Its quality is described by fill power, a number typically ranging from around 450 to 900, measuring how many cubic inches an ounce of down expands to fill. Higher fill power means more warmth per gram. Down excels in cold, dry conditions.
Its weakness is water. When down gets wet it clumps, the air pockets collapse, and it loses much of its insulating ability. Synthetic fills keep insulating when damp, breathe reasonably well, dry faster, wash more easily and generally cost less.
For a Dutch winter — grey, damp, rarely deeply cold, frequently drizzling on the way to school — synthetic is usually the more practical choice. Down makes more sense for a sledging holiday in the Alps than for a Tuesday in Amsterdam-Noord.
| Down | Synthetic | |
|---|---|---|
| Warmth for the weight | Best in class | Bulkier for the same warmth |
| When it gets wet | Clumps, loses loft and warmth | Keeps insulating |
| Washing | Fussy, slow to dry | Straightforward |
| Cost | Higher | Lower |
| Animal welfare question | Look for RDS certification | None; usually petroleum-based fibre |
If you do buy down, look for the Responsible Down Standard (RDS) on the label. Administered by Textile Exchange, it certifies the full supply chain from farm to finished garment and prohibits live-plucking and force-feeding. Without it, there's no practical way to know where the fill came from.
The coat is only the outer third of the system
A common mistake is asking one coat to do everything. It can't. Warmth in winter comes from a stack, and the coat is only the top of it.
- Base layer — sits against the skin and moves moisture away from it. A child who gets sweaty running around and then stands still at the school gate is a child who gets cold. Cotton against the skin is comfortable and breathable; merino handles damp better on the coldest days.
- Mid layer — this is where most of the warmth actually lives. A knit jumper, a fleece, a light quilted vest. Easy to add and remove as the day changes.
- Outer layer — blocks wind and rain. In the Netherlands, windproof and water-resistant matter far more than sheer insulation.
The advantage of a stack is that it adapts. A 4°C dry morning and a 4°C wet, windy morning need very different things, and one heavyweight coat can only answer one of them. Two moderate layers also pack down far smaller for the walk home when the sun comes out.
Bulky coats and car seats don't mix
This is the part of a winter coat conversation that most deserves the space. The American Academy of Pediatrics advises that bulky clothing — including winter coats and snowsuits — should not be worn underneath a car seat harness.
The reason is the same property that makes a puffer warm. The fill traps a large volume of air, and in a crash that air compresses instantly. A harness that felt snug over the coat is suddenly loose against the child's body, leaving room for them to move forward against the straps.
Child passenger safety educators recommend a simple check, often called the pinch test:
- Put the coat on your child and buckle them into the seat as normal.
- Tighten the harness until you can't pinch any excess webbing between thumb and forefinger.
- Without touching the harness setting, unbuckle, take the coat off, and buckle them back in.
- Pinch again. If you can now gather slack, the coat is too bulky to wear under the harness.
The workarounds are easy. Buckle the child in first, then put the coat on backwards over the top, arms through the sleeves — warm, and entirely outside the harness. For babies and smaller children, a blanket over the top after buckling does the same job. Thin fleece layers generally pass the pinch test where puffers don't, which is another argument for the layering approach.
Buying one coat instead of three
The most sustainable coat is the one that gets worn for two winters and then handed on. A few things make that likelier: a neutral colour that doesn't date or read as belonging to one child in particular, reinforced cuffs and elbows, a full-length zip with a chin guard, and generous seam allowances that can be let out. Detachable hoods and removable liners stretch the season at both ends.
Check the second-hand market before the new one. Outerwear is the category where used buying makes the most sense — coats are typically worn a few hours a day for one season, so a well-made one arrives barely touched. Our Twice Loved pieces exist for exactly this reason.
FAQ
How many sizes up should I buy a kids' winter coat?
One. That leaves room for growth and for a jumper underneath. Two sizes up compromises the fit at the neck, wrists and hem, where a coat needs to seal to keep warmth in.
Can my child wear their winter coat in the car seat?
Not if it's bulky. The AAP advises against winter coats and snowsuits under a car seat harness, because the fill compresses in a crash and leaves the harness loose. Use the pinch test to check, and put the coat on backwards over the buckled harness instead.
Is down or synthetic better for a Dutch winter?
Synthetic, for most families. It keeps insulating when damp, dries faster and washes more easily — all of which matter more in a wet, mild winter than the extra warmth-to-weight that down offers.
What does fill power mean?
It measures the quality of down: how many cubic inches one ounce of it expands to fill, usually between about 450 and 900. Higher fill power gives more warmth for less weight and bulk.
How do I know the down was ethically sourced?
Look for the Responsible Down Standard (RDS) label. It certifies the chain from farm to garment and prohibits live-plucking and force-feeding. Unlabelled down is untraceable.
Does my child need more than one coat?
Usually two are enough: a light waterproof shell for mild, wet days and one insulated coat for genuinely cold ones. Layers underneath cover everything in between, which is cheaper and more flexible than owning a coat for every temperature.