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A Size 12 at Nike Isn't a Size 12 at Adidas. Why Not?

Although numerical sizing — 12, 11, 10, etc. — is a universal key, numerical sizes from brand to brand are rarely the same.

young man in shoes store
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Size matters, especially when it comes to footwear. If you have particularly wide or narrow feet, are between sizes or have one foot that's slightly longer than the other, you know the drill: you can wear one size from one brand, but the same size from another brand is... off — it's too small or too tight, leaving your toes cramp or your heel hurting.

These kind of discrepancies aren't rare. For most folks, a little bit of guessing goes into the purchase of every an item that's one-size-fits-all — even then, who knows if it'll fit. Needless to say, shopping shouldn't be this hard. Unlike vanity sizing, though, which is akin to size inflation or "the phenomenon of ready-to-wear clothing of the same nominal size becoming bigger in physical size over time," differences between a size 12 from Nike and a size 12 from Adidas stem from their respective design choices — to have a smaller profile, help you run faster, stand more comfortably and so on and so forth.

There is a baseline these brands can follow, though: the Brannock Standard, which is measured using a Brannock device. First designed in 1927, the device measures with impressive accuracy, consistency and, above all else, ease. So, based on this guideline, we can figure out whether some of the top brands run big or small.

brannock device
measuring equipment for shoe fitting
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Do Converse run big or small?

According to the brand, both the Chuck Taylor All Star and the Chuck 70 run a half-size large. So, if you usually wear a size 7 — and measure out to a size 7 on the Brannock device — you should order a size 6.5. Some of the brands basketball-focused styles — the All Star Pro BB and BB EVO — run a half size small. Then, a size 7 should order a 6.5.

man wearing converse shoes

Do Crocs run big or small?

Crocs are true to size, but the Classic Clog does run a little wide. So, if you're between sizes or have narrow feet, it's probably best to try a pair on in person rather than ordering them online.

someone wearing pink crocs

Do Vans run big or small?

Vans run true to size, but if you prefer a looser fit or have wide feet, you should consider sizing up. My size 12 Vans Authentics are snug, and I'm a true size 12. If you're a 12.25, for example, a 12.5 would be a more comfortable choice.

vans shoes on a drum set

Do Birkenstocks run big or small?

Birkenstocks mold to your feet over time. Plus, both straps are adjustable. So, order true to size. Even if you plan to wear them with socks only, the straps help make room for even the thickest ones.

person wearing white birkenstocks

Do Doc Martens run big or small?

Generally, Doc Martens fit true to size, but they might feel a little big after the break-in period as is the case with most boots that will stretch and mold to your foot. The 1460s run a little large, for example, but Doc Martens doesn't sell half sizes. If you can wear either an 11 or a 12, for example, go with an 11.

person wearing black doc martens boots
Doc Martens

Do UGGs run big or small?

UGG boots run big, meaning you should size down by a half or full step. UGGs are made from sheepskin, a material that stretches with wear. If you are a 12 and your order a 12, they'll feel like a 12.5 or 13 after a few months wear. You want to work your way to a 12, not out of it.

someone wearing ugg boots on a couch

Do Nikes run big or small?

Nikes notoriously run small, and Nike might've realized it a few years back. They launched the Nike Fit app, where AR and AI technologies scan your foot and find your perfect Nike size. The app has since shuttered, but customers can feel confident ordering true to size. Some customers have complained that Nikes run narrow, and that may be the case for folks with wide feet. Standard feet? True to size.


Do Adidas run big or small?

Adidas sneakers run true to the Brannock Standard — a.k.a. true to size. Their size chart confirms it. But it also makes mention of those between sizes: "For a tight fit, go one size down. For a loose fit, go one size up." This is especially pertinent to the Stan Smith style.

man and woman wearing adidas stan smith shoes

Do Timberlands run big or small?

Timberland's most popular boots run big. As such, you should size a half-size down if you're a standard size — 7 to 6.5, for example. If you're barely a 7, though, you might be able to squeeze into a 6. Their bots are hard-wearing, meaning you'll have them for a long time. You don't want them to feel stretched out after a few seasons.

someone wearing timberland's boots

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