Why Is My Shoe Size Different in Every Brand?

Why does my shoe size change from brand to brand?

Three reasons, and they stack:

• Every brand has its own lasts. A last sets the shoe's length, width, toe shape, arch and heel. Two brands' size 9s are built on two different lasts, so they're different shapes, not just different lengths.
• No one enforces a standard. Shoe size systems aren't fully standardized, and the US and UK systems aren't formally standardized at all. Brands decide how their sizes and widths grade from one to the next, and even width letters vary: one maker's E isn't necessarily another's.
• The systems measure different things. UK and EU sizes count steps along the shoe's last. Mondopoint, used for ski boots and some work footwear, is your foot length in millimeters. Converting between them is never exact, which is why conversion charts disagree with each other.

The practical result: your size is a starting point for each new brand, not a fact about your foot. What does carry over is your foot's measurements, which is where a fitting starts.

How much bigger is a half size?

Less than most people think. The steps in each system:

A half size is a small change in length and a very small change in room across your foot. That's why going up a half size rarely fixes a shoe that pinches.

Should I go up a half size or up a width?

If the length is right and the shoe feels tight across the ball of your foot, go up a width in the same size. Here's why. In traditional shoe grading, each step up in width adds about 1/4 inch of girth (the distance around the ball of the foot), while each whole size adds only about 1/8 inch of girth. A half size, then, adds about 1/16 inch around your foot, a quarter of what one width adds, and puts most of its change into length instead.

Take a common case: you try an 11D and it's tight. An 11 2E keeps the ball of your foot in the right place and gives you real room across it. An 11.5D mostly makes the shoe longer, which moves the shoe's flex point forward of your foot's and can let your heel slip, while barely changing the squeeze. The "go up a half size, down a width" swap you'll see online works out the same way: it trades a lot of width for a little length, so it isn't an even swap.

Two exceptions. If it's the tips of your toes that are crowded rather than the ball of your foot, check the length (the guide to how shoes should fit shows how) and the toe-box shape (see wide toe box shoes) before you change width. And these grading figures are a tradition, not a rule: a given brand's last can differ, so try the wider width on rather than assuming.

How do I convert women's shoe sizes to men's?

Most brands put a women's size about 1.5 above the men's size for the same length, so a women's 8.5 is roughly a men's 7. KEEN's own size guide uses exactly that comparison. But it isn't universal: some sizing scales use a difference of 1, and Birkenstock's chart puts women's and men's US sizes 2 apart for the same EU size (women's US + 31 and men's US + 33 give the EU size). Always check the chart of the brand you're buying.

Length isn't the only difference. Men's shoes are cut wider than women's at the same length: a men's standard width is D, which is a women's wide. KEEN says it plainly: a men's size will fit as a women's wide. That makes a men's shoe one way to get extra width in a style that doesn't come in a women's wide.

US to UK: a men's US size is usually the UK size plus 1. For women it's usually plus 2, but makers vary here too.

Is an EU 42 the same in every brand?

No. An EU size counts 2/3 cm steps along the brand's last, and every brand's last is different, so two brands' EU 42s can fit quite differently. Many European brands also make whole EU sizes only. Dansko, for example, sizes by whole EU sizes, so a US half size can fall between two of its sizes. When that happens, the brand's own guidance is the tiebreaker: Dansko's is to leave about a pinky finger's width of space between your heel and the back of the shoe, and Birkenstock's is about 1/4 inch of space around your foot in the footbed.

Is "wide" the same in every brand?

The US letters mostly line up: for women, B is standard and D is wide; for men, D is standard and 2E is wide. (A women's D and a men's D are not the same width.) But brands don't all use the letters, and some use them differently. Here's how a few brands label width, from their own size guides:

Brands change their size ranges, and not every style comes in every width. Check the size chart for the exact shoe.

For what the US letters mean and how to tell if you need a wide, see how shoes should fit.

How do I find my size in a brand I've never worn?

1. Get measured, both feet, later in the day. Feet swell as the day goes on, and most people are a little different left to right; fit the larger foot. You want three numbers: heel-to-toe length, width, and arch length (heel to the ball of your foot), which is what places the ball of your foot at the shoe's widest point.
2. Use the brand's own size chart, not a generic conversion chart. Generic charts online often contain errors, and they can't know any one brand's lasts.
3. Read the brand's own fit notes. Some say outright that a style runs large or small, or which width to choose; that beats a stranger's review.
4. Fix width with width and length with length. Tight across the ball of the foot: go wider in the same size. Toes at the end or heel slipping: the length is wrong.
5. Try it on with the socks and insoles you'll wear. A thicker sock or a custom orthotic takes up room a size chart can't account for.