The fastest way to find someone's clothing size without asking is to read the label in something they already own and wear often. It takes about thirty seconds and it's more reliable than anything they'd tell you.
People misreport their own sizes constantly, not dishonestly, just out of date. The label in the jumper they wear every week is current. Their memory of what they bought in 2019 is not.
1. Read the label in something they wear a lot
Pick a garment that fits them well and that they've chosen for themselves. Then photograph the label rather than trying to remember it, because you will not remember it.
Sizes hide in different places depending on the item:
| Item | Where the label is |
|---|---|
| T-shirt, top | Back neck, or side seam |
| Jumper, knitwear | Back neck, or side seam |
| Jeans, trousers | Back waistband patch |
| Shirt | Inside the collar band |
| Coat, jacket | Inside collar, or pocket lining |
| Dress | Back neck, or left side seam |
| Bra | Near the hook, or centre front |
| Shoes | Inside the tongue, or the insole |
| Hat | Inside the sweatband |
Two rules while you're in there. Check more than one item, because every wardrobe contains something that was a gift, never fitted, and was too awkward to return. Three garments that agree beats one that doesn't. And put it back exactly as you found it, folded the way it was folded. The tell is never the size, it's the jumper that's suddenly on top of the pile.
If the label has washed out, which happens to the favourite things first, try the same brand's other items or move on to a different garment. Don't guess from a blank label.
2. Measure a shoe rather than trusting its size
Shoe sizes are the least reliable numbers in clothing, so measure the insole in centimetres and shop by that where you can. A UK 8 in one brand is a UK 8.5 in another, and trainers run differently from boots in the same brand.
To measure: take out the insole if it's removable, lay it flat, and measure heel to longest toe in centimetres. If it doesn't come out, measure the inside of the shoe from the back of the heel to the tip.
Then check the size printed inside the tongue or on the insole anyway, and note the brand alongside it. "UK 8 in Adidas" is useful. "UK 8" on its own is a starting point.
3. Ask someone who already knows
Their mother, their partner, their flatmate, or whoever does the laundry. One text, and the surprise stays intact.
Pick your accomplice for discretion rather than closeness. The person who knows the answer instantly is sometimes also the person who cannot keep a secret for eleven days.
Tell them what you're buying, too. They'll often know something more useful than the number: that the shoulders are the problem, that they've stopped wearing that brand, that someone else already bought one.
4. Check the shared order history
If you share a household, an address, or a delivery account, past orders are sitting there with sizes attached. Amazon order history, a shared Prime account, a package that arrived last month with a label still on it.
Returns are the goldmine. A bag by the door waiting to go back tells you both the brand and the size that didn't work, which is nearly as useful as the one that did.
Stay on the right side of this one: your own shared account and parcels in your own hallway, not someone's private accounts.
5. Compare against yourself
If you're roughly the same build, hold the garment up against your own. It's crude, and it's better than nothing.
Better version: get them to try on something of yours in an ordinary moment. Lending a coat when it's cold outside is not suspicious. Noting that it was slightly big on them is free information.
6. Ask a question that isn't the question
You can get close without ever saying "what size are you?" if you ask about something adjacent.
Things that work:
- Complain about a brand's sizing and ask if they've had the same problem. People answer with their size unprompted.
- Send them a link and ask if they think it would fit you. They'll often compare it to themselves.
- Talk about a shop while you're both in it. "Do you buy these here?" gets you the brand, and the brand narrows the size.
- Mention returns. "I always have to size up in these" invites the same admission back.
Things that don't work: asking directly and pretending it's for a survey, or asking their size "for a group order" when there is visibly no group order.
What doesn't work: guessing from how they look
Eyeballing a size is unreliable even for people who work in clothing, and it's worse when you know the person, because you picture them as they were rather than as they are.
Height and weight tell you almost nothing on their own. Two people at the same measurements wear different sizes depending on shoulders, proportion, and what they like the fit to be. Someone who buys everything oversized wears a size that has nothing to do with their body.
Don't do it if you can avoid it. If you can't, see the last section.
Why size numbers don't match between brands
Clothing sizes are not a standard. They're a marketing decision, and they drift.
Two things to know before you buy.
Vanity sizing is real. The number on a garment has crept downward over decades, unevenly, by brand and by country. The same body wears a different number in a high-street shop and a designer one.
Country conversions are only approximate. For women's clothing, the usual rule is UK = US + 4, and EU = UK + 28, so a US 6 is a UK 10 is an EU 38. Treat that as a starting point rather than a fact, because brands ignore it freely. For men's shirts and trousers, sizes are usually in inches and travel better between countries, and EU jacket sizing is roughly the chest in inches multiplied by two.
So write down the brand with the size, every time. A size without a brand is half a piece of information.
What to buy when you can't find out
Buy something that doesn't need a size, or buy from somewhere that will exchange it without a fuss.
Sized loosely enough to be safe:
- Scarves, gloves, hats, socks
- Bags, belts sold by S/M/L, wallets
- Oversized knitwear and sweatshirts, one size up
- Robes and pyjama sets, which are cut generously
- Jewellery, though not rings. For those, see how to find someone's ring size without asking
If you must guess a real garment, size up rather than down. A gift that's slightly big is a gift. A gift that's too small is a comment on their body, whether you meant it that way or not.
Then check the returns policy before you order. Confirm they can exchange it without you, include the gift receipt, and say plainly that you kept it so they can swap the size. Nobody has ever been offended by that.
Write it down while you still know it
You'll do the wardrobe reconnaissance in September, feel briefly like a detective, and by December have no idea whether it was a 38 or a 40.
So put it somewhere permanent the moment you find it, with the brand and the date you checked. Sizes change, and a number from four years ago is a guess.
What matters is that it's attached to the person rather than floating in a note you'll never scroll back to. Clothing size is rarely the only detail worth keeping: shoe size, the allergy, the brand they've sworn off, the thing they mentioned wanting in a shop in March. Keeping all of it in one place for a whole year is its own small skill.
Presented keeps those against each person alongside their birthday, so they're waiting when the date arrives instead of being reconstructed from memory in a hurry. That's most of what it's for.
The app is optional, the habit isn't. Photograph the label and write the number down, so that future you, buying a coat with four days to spare, has less work to do.