Duke is a golden retriever puppy, which means Duke is a moving target. Four months old, all paws and elbows, and roughly the size of a slightly different dog every two weeks. When his family wrote to us asking which size to order for his first costume, they asked the question almost everyone asks:
Should we size up so he can grow into it?
It's a reasonable instinct. It's also the single most common reason a pet costume ends up folded in a drawer instead of showing up in photos. Here's how we answered them — and how to measure your own dog properly, puppy or not.
Why "sizing up to grow into it" backfires
A costume hoodie isn't a winter coat. It works precisely because it sits close enough to the body to hold its shape: the hood stays where it belongs, the sleeves move with the front legs, the back seam follows the spine.
Go one size too big and none of that holds. The hood slides sideways and covers an eye. The chest opening gapes and snags on furniture and doorframes. The sleeves bunch at the elbow, and your dog spends the evening trying to shake the whole thing off instead of wearing it.
Dogs are quick to tell you when clothing is wrong. A loose hoodie reads to them as something stuck to me. A well-fitted one mostly disappears — which is the entire goal.
So for a growing puppy, the honest answer is this: buy for the dog standing in front of you. Fit now beats fit later, every single time.
How to measure your dog in two minutes
You need a soft tape measure — the fabric kind from a sewing kit, not a retractable metal one — and ideally a second person holding treats. Only two numbers matter.
Chest. Wrap the tape around the widest part of the ribcage, just behind the front legs. Snug, not tight: you should be able to slide two fingers underneath. This is the number that decides the size.
Back. Measure along the spine, from the base of the neck where a collar sits to the base of the tail. This tells you whether the length will sit right.
Measure your dog standing up, not sitting. A sitting dog compresses in the chest and stretches in the back, and you'll get two numbers that describe a dog who doesn't exist.
The chart, in plain numbers
- XS — Chest 12.5" / Back 8" — teacup breeds and kittens, around 2–4 lbs
- S — Chest 15" / Back 10" — small breeds and most adult cats, around 4–8 lbs
- M — Chest 17.5" / Back 12" — small-medium breeds and large cats, around 8–15 lbs
- L — Chest 19.5" / Back 14" — medium breeds, around 15–25 lbs
- XL — Chest 22" / Back 15.5" — medium-large breeds, around 25–35 lbs
- 2XL — Chest 24.5" / Back 17.5" — large breeds, around 35–50 lbs
Weights are a sanity check, not the rule. Two beagles at the same weight can be built completely differently. Trust the chest measurement.
And the rule that saves the most orders: if your dog falls between two sizes, size up — by one size, once. Not two sizes. Not "he'll be bigger by Christmas."
Costumes that measure differently
The chart above covers the fleece hoodies. Three pieces in the range fasten around the neck rather than sliding over the front legs, so the neck measurement decides the size instead of the chest — take it around the base of the neck, where a collar sits.
- The bat wings pet costume comes in S, M and L, covering chests from 36 to 85 cm, for cats and dogs alike.
- The spider pet costume comes in S and M only — cats and small dogs.
- The Santa Claus dog costume runs XS to XL and does put the front legs through sleeves, so measure both chest and neck for that one.
The same rule applies throughout: measure the dog you have today, and size up once if he lands between two.
What we actually told Duke's family
Duke measured 21 inches around the chest. That put him at the top of XL, close enough to 2XL that his family were already reaching for the bigger one.
We asked them three questions instead.
1. When do you want to use it? They wanted photos in October, at a neighborhood thing, in about four weeks. Four weeks of golden retriever puppy is a real amount of growth — but not a full size of it. XL would still fit.
2. Is he still gaining weight fast? He was. Which meant that whatever they bought, he would outgrow it. A golden retriever finishes well past 50 lbs, which is past the top of our chart. There is no size they could have bought that Duke would still be wearing next autumn. Once that's on the table, "buying for later" stops being a strategy and becomes a guess.
3. Is he relaxed about being handled? He is — four-month-old golden, sits still for anything involving attention. A confident dog is more forgiving of a snug fit than a nervous one. If Duke had been anxious, we'd have pushed him up to 2XL and accepted a slightly loose hood, because for a nervous dog, loose is less alarming than close-fitting. If that's your dog, our guide on helping a nervous pet feel confident in their first costume is the better starting point.
They ordered XL. Duke got the Banana — soft yellow fleece with a peeled-banana hood, which on a golden retriever puppy is very nearly too much.
Notice where the hood sits: clear of the eyes, ears free, the drawstring doing its job. That's what the right size looks like. He wore it for an hour on the first try and fell asleep in it, which is the review we care about most.
If your puppy is between sizes right now
Three practical calls, depending on which situation you're in:
You need it within a month. Buy for today's measurement. A month of growth won't cost you the fit.
You need it in two to three months. Size up once. A puppy who's currently mid-L will be comfortably XL by then.
You want something that lasts a year. With a large breed, that isn't really a sizing question — it's two costumes, or one costume and honest expectations. With a small breed who'll finish near her current weight, buy her adult size now and take the slightly roomy fit for a few weeks.
One note on timing
If you're planning ahead for the holidays, measure now rather than in December — a puppy measured in September is a different dog by Christmas, and that's the whole point of this article.
It also matters for availability. Frog, Carrot and Banana ship from our US warehouse in 5–8 business days. Apple, Heart, Cabbage and Reindeer are restocking and currently ship in 2–3 weeks, so if the Reindeer is the one you want for December photos, order it earlier than feels necessary.
The Halloween and Christmas pieces — bat wings, spider, and the Santa riding dog costume — ship from a different warehouse again, in 7 to 14 business days. Order at least three weeks before Halloween, and by December 5 for Christmas.
All seven fleece designs come in XS through 2XL in soft polar fleece, with an adjustable hood drawstring and stretchy sleeve cuffs — and they're machine washable, which matters more than it sounds like it does once a puppy is involved.
Got two pets? Add a second costume in any design and any size and 15% comes off automatically at checkout.
Measuring a cat instead? The cat sizing guide walks through the same two numbers on a smaller frame.
Measure the chest. Trust the number. Size up once if you must. That's the whole guide.