You’re standing in the middle of a crowded shoe aisle, or worse, you’ve got sixteen tabs open on your phone trying to snag those limited-edition sneakers before they sell out. You see it. Size 42. Your brain does that quick, frantic math we all do when we’re used to US or UK sizing. Is it a 9? Is it an 8.5? Honestly, it depends on who you are and what you’re putting on your feet.
Size 42 is the "middle child" of the footwear world. It’s right at that awkward junction where men’s and women’s sizing charts start to overlap and cause chaos.
So, what shoe size is a 42 in the real world?
If you’re shopping for men’s shoes, a European size 42 generally translates to a US size 9.
But wait.
If you are looking at women’s shoes, that same 42 suddenly jumps up to a US size 10.5 or 11. This isn't just some random quirk of the fashion industry; it’s rooted in how different regions measure the physical last of the shoe. While the US system is based on barleycorns (an ancient, slightly ridiculous unit of measurement), the European system uses the Paris Point. One Paris Point is exactly two-thirds of a centimeter.
It sounds precise. It’s actually kind of a mess.
The Men’s vs. Women’s Divide
Most people assume a 42 is a 42. It isn't. Brands like Nike, Adidas, and Birkenstock all treat that number with a slightly different level of respect. For example, in a pair of Birkenstocks—the ultimate "size-sensitive" shoe—a 42 is almost always a men’s 9 or 9.5. However, if you’re a woman with a larger foot looking at European luxury brands like Gucci or Prada, a 42 is the holy grail of "extended sizing," usually fitting a US women's 11.
There’s a biological reality here too. Men’s feet are typically wider. A men’s 42 is built on a "D" width last. A women’s 42 is often built on a "B" width last. If you’re a guy with narrow feet, you might actually find a women's 42 fits better, but good luck finding a style that isn't adorned with something you might not want.
Why brands can't agree on what 42 means
Ever noticed how a 42 in a Common Projects sneaker feels like a boat, but a 42 in a Zara dress shoe cuts off your circulation?
It’s about the "allowance."
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European sizing is technically a measure of the internal length of the shoe, but every designer adds a different amount of "wiggle room" or "toe spring." High-end Italian designers often use a longer, tapered toe. This means the 42 is technically the right length, but your foot stops an inch before the tip of the shoe.
Then you have the UK vs. US vs. EU triangle of confusion.
- A EU 42 is roughly a UK 8.
- It's a US Men's 9.
- It's roughly 26.5 to 27 centimeters long.
But if you look at a brand like Hoka or New Balance, they might list a 42 as an 8.5 US. Why? Because they prioritize performance fit. They know that when you run, your foot expands. If they sold you a "true" 42 that translated to a tight 9, you’d lose a toenail by mile four.
The "Paris Point" and the math behind the leather
Let's get nerdy for a second. The formula for European shoe sizing is actually $Size = \frac{3}{2} \times L$, where $L$ is the length of the shoe last in centimeters.
If you do the math for a size 42:
$42 = \frac{3}{2} \times L$
$L = 28\text{ cm}$
You might think, "Wait, my foot isn't 28 centimeters long!" You're right. The shoe last (the mold the shoe is made on) has to be longer than your foot. This is where the 1.5 to 2 cm of "clearance" comes in. If your foot is exactly 26.5 cm, a 42 should, in theory, be your perfect home.
But leather stretches. Synthetics don't. A 42 in a Martens boot is a heavy-duty commitment. It’s going to feel massive until that leather softens and molds to your heel. Conversely, a 42 in a knit Allbirds sneaker might feel like a sock.
Does gender-neutral sizing help?
Lately, we’ve seen a massive shift toward "unisex" or "gender-neutral" sizing, especially in the streetwear scene. Brands like Converse and Vans have been doing this forever. On the bottom of a Chuck Taylor, you’ll see several numbers.
A EU 42 in a Converse All-Star is usually labeled as a Men’s 8.5 and a Women’s 10.5.
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Wait—didn't I just say a 42 is a Men’s 9?
This is the "Converse Trap." Converse runs notoriously large. Most sneakerheads will tell you to "size down half a size" in Chucks. So, their 42 actually fits like a 42.5 or a 43 in other brands. It’s enough to make you want to go barefoot.
Regional variations you need to know
If you are buying shoes from a brand based in Spain or Portugal, they tend to run slightly narrower than brands from Germany or Denmark.
Think about the foot shapes in those regions. Mediterranean feet are often characterized by lower volume. Scandinavian feet? Broad and sturdy. If you're looking at a 42 from Ecco (Danish), you’re going to get a lot more room in the toe box than a 42 from Magnanni (Spanish).
Then there’s the Japanese (JP/CM) system, which is honestly the only one that makes sense. It’s just the length of your foot in centimeters. If you see a shoe labeled "26.5" or "27," that’s your size 42. It’s simple. It’s logical. Naturally, the rest of the world refuses to use it.
The sock factor
Don't laugh. It matters.
If you're sizing a 42 for a winter boot, you're likely wearing thick wool socks. That can add half a size to your foot's volume. A 42 that fits perfectly in June with no-show liners will be a torture chamber in December with Smartwools.
Always measure your feet in the afternoon. Why? Because you’ve been standing on them all day. They’re swollen. They’re at their "max capacity." If a 42 feels tight at 4:00 PM, it’s too small. No "breaking them in" is going to fix a fundamental lack of millimeter clearance.
How to measure your foot to see if you’re actually a 42
Forget those metal Brannock devices for a minute. You can do this at home with a piece of paper and a wall.
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- Place the paper on a hard floor, flush against a wall.
- Stand on the paper with your heel touching the wall.
- Mark the tip of your longest toe (it’s not always the big toe!) with a pencil.
- Measure the distance from the edge of the paper to that mark in centimeters.
If your measurement is between 26.3 cm and 26.8 cm, you are a "True 42."
If you’re over 27 cm, you need to start looking at a 43. If you’re under 26 cm, you’re likely a 41.
Actionable steps for your next purchase
Buying shoes online is a gamble, but you can rig the game in your favor.
First, check the "Size Guide" on the specific brand's website. Never rely on a generic conversion chart you found on Pinterest. Brands like Nike have spent millions of dollars on fit-testing; use their specific data.
Second, look for the "Last" information. If a shoe description mentions it's built on a "narrow last" or has a "sport fit," and you're a 42, you might want to consider the 43.
Third, read the reviews specifically for the word "True to Size." If twenty people say "runs small," believe them. A 42 is not a universal constant; it’s a suggestion.
Fourth, consider the "Mondopoint" if you're buying ski boots or technical gear. This measures width and length. A 42 in a ski boot is usually a 27.0 or 27.5.
Ultimately, the number on the tongue of the shoe matters less than the sensation in your arch. If you find yourself constantly debating between a 41 and a 42, you are likely what we call a "tweener." In that case, always prioritize the 42. You can add an insole to a shoe that's a bit big, but you can't stretch a shoe that’s fundamentally too short. Your toes will thank you.
Stop stressing about the conversion and start measuring your actual foot length in centimeters. It is the only way to survive the wild west of international footwear.