Quick Answer: Secondhand sizing is meaningless because sizes have drifted for decades and vary by brand and era. Buy to five measurements instead: shoulder to shoulder, pit to pit, waist, sleeve length, and total length. Measure your best-fitting garment flat and compare to the listing. Shoulder width is the one that cannot be altered economically, so treat it as the pass or fail number and treat everything else as negotiable.

The blazer is your size on the label. It arrives and the shoulders finish two inches past yours, which no alteration is going to fix affordably.

The listing had the answer in it. It just was not in the size field.

Why is secondhand sizing so unreliable?

Because a size label describes a brand and an era, not a body.

Sizes have drifted steadily for fifty years. A garment labelled size 12 from the 1970s is roughly a modern size 6 to 8, and the drift is continuous rather than stepwise, so there is no reliable conversion table across decades.

Brands within the same year differ enormously. Two current size 10 jackets from different labels can differ by two inches at the bust and an inch at the shoulder. Vanity sizing makes this worse and it is not standardised in any direction.

Country of origin adds another layer. UK, US, EU, and Japanese sizing all use different scales, and secondhand listings frequently report whichever label is printed without noting the system.

Garments also change with wear. A wool jacket worn for years takes on the previous owner’s shape, and knitwear stretches or shrinks depending on how it was washed. The label describes the original garment, not this one.

And alterations are invisible in a listing. A previously altered piece may have taken-in seams or a shortened sleeve that make it fit nothing like its label.

Measurements sidestep all of it, because a measurement describes the actual object in front of the seller.

Which five measurements actually matter?

Shoulder to shoulder is the most important and the least negotiable. Measured across the back from one shoulder seam to the other. If this is more than half an inch off, do not buy — shoulder alterations cost sixty to a hundred dollars and are not economic on a thrifted piece.

Pit to pit tells you the chest. Measured flat across from armpit seam to armpit seam. Double it for the full circumference. Two to four inches of ease beyond your body measurement is normal for a jacket; less for a fitted top.

Waist, measured flat at the narrowest point. This is the most alterable of the five — a tailor can take in a waist for twenty to forty dollars — so treat a slightly large waist as an opportunity rather than a problem.

Sleeve length from shoulder seam to cuff. Easily shortened, difficult to lengthen. A slightly long sleeve is fine; a short one is usually terminal.

Total length from the base of the collar to the hem. This decides proportion, and on a coat or a jacket it is the number that determines whether the piece works on your frame at all.

One more worth requesting on trousers: the rise. Front rise from crotch seam to waistband. Nothing affects how trousers sit more, and it is almost never listed.

What Nobody Tells You About Measuring at Home

Measure a garment you already own and love, not your body. This is the whole trick and almost nobody does it. Your body measurement plus a guess at ease is far less accurate than the actual flat measurement of something that already fits.

Lay the garment flat on a hard surface, buttoned and smoothed. Do not stretch it. A measurement taken on a soft bed reads an inch large every time.

Keep a note on your phone. Five numbers for a jacket, four for trousers, three for a top. Once written down, this file does years of work and it makes every resale platform usable.

Record the numbers for two versions of each category — a fitted blazer and a relaxed one, for instance. Ease preferences differ by style and one set of numbers cannot cover both.

Ask for a missing measurement. Most private sellers will measure on request, and a seller who will not is telling you something useful.

Watch for measurements given as body size rather than flat. A listing saying bust 38 might mean the garment measures 38 around or that it fits a 38 bust. Ask which, because the difference is the entire ease allowance.

The surprising part: this takes fifteen minutes once and it removes almost all resale return risk permanently.

How do I judge condition and value from photos?

Ask for a photo in daylight, flat, front and back. Styled photos on a hanger hide the shoulders and the drape. A flat photo shows the real shape.

Look for shine at the elbows, seat, and knees. Polished patches on wool are permanent fiber damage. Zoom in on those three areas before anything else.

Check the underarms specifically. Deodorant damage and yellowing on light fabrics is the most common irreversible flaw, and it is the area sellers photograph least.

On knitwear, ask about pilling and small holes. A single moth hole is repairable; a scatter of them means eggs and it is not worth the risk to the rest of your wardrobe.

Look at the hardware. Original buttons, a smooth zip, and intact lining all indicate a garment that was cared for. A replaced zip usually means it was worn hard.

Check the fabric composition photo. Natural fiber content is the main reason to buy secondhand at all, and a listing that will not show the care label is often hiding a polyester blend.

And factor alterations into the price. A forty dollar blazer plus a thirty dollar waist adjustment is still an excellent buy; a forty dollar blazer that needs a hundred dollar shoulder is not.

FAQ: Online Resale Questions, Answered

What is the single most important measurement?

Shoulder to shoulder on anything with a set-in sleeve. It is the one measurement that cannot be altered economically, and a shoulder more than about half an inch too wide will make the whole garment look borrowed regardless of how well the rest fits.

How much ease should I allow?

It depends entirely on the garment. Compare to a piece you already own in that category rather than to your body, and the ease question answers itself. That is why measuring your own garments matters more than measuring yourself.

How do I convert vintage sizes?

Do not try. The drift is continuous and brand-specific, so any conversion chart is an approximation at best. Ignore the label completely on anything more than about fifteen years old and work only from measurements.

Are returns usually possible on resale platforms?

It varies by platform and many private sales are final. That is precisely why measurements matter more here than in retail — you are usually committing at the point of purchase.

What flaws are worth accepting?

A missing button, a loose hem, a waist that is too large, and a sleeve that is too long are all cheap fixes. Shoulder width, underarm staining, moth damage, and shine on wool are not worth taking on at any price.

TL;DR: Ignore the label, read the numbers.

• Sizes have drifted for fifty years and vary by brand, country, and era. The label tells you nothing.
• Five numbers matter: shoulder, pit to pit, waist, sleeve, and total length.
• Shoulder width is pass or fail. Everything else is negotiable at a tailor.
• Measure a garment you love, not your body. Fifteen minutes once, useful for years.
• Zoom in on elbows, seat, and underarms. Those flaws are the irreversible ones.
• Price the alteration in. Forty dollars plus a thirty dollar waist is still a great buy.

Go measure the jacket that fits you best and put the numbers in your phone. That file is the whole system.