If you have ever ordered a pair of barefoot shoes in "your size" and found them oddly short, or a full thumb-width too long, you are not alone. Sizing questions are the single most common thing readers ask us about, and the confusion is understandable: an EU 42 is not the same length in every brand, a US 9 doesn't map neatly onto any EU size, and barefoot shoes add one more variable that conventional shoes don't have — deliberate room for your toes.
The good news is that you don't need to memorize anything. Once you understand what a size chart is actually telling you, you can read any brand's chart — ours included — and land on the right size on the first try. Here is the method I use, step by step.
Why your "normal" size doesn't always work
Shoe sizes were never a universal standard. Every brand builds its shoes around a last — the foot-shaped form the shoe is constructed on — and every brand's last is a little different. Two shoes labeled EU 42 can differ by several millimeters inside, because the label describes the last, not your foot. Style matters too: a pointy dress shoe and a foot-shaped barefoot shoe in the same nominal size leave completely different amounts of usable room for your toes.
This is why serious barefoot brands publish their size charts in centimeters or millimeters of internal length. Centimeters are the only honest unit in footwear: your foot is a physical object with a measurable length, and the inside of a shoe is a physical space with a measurable length. Match the two, and the label on the box stops mattering.
Step 1: Measure your feet properly
Everything starts with an accurate foot measurement. You need a sheet of paper, a wall, a pencil and a ruler — nothing else.
How to do it
- Measure in the evening. Feet naturally swell over the course of the day, and the difference can be close to half a size. A shoe sized to a morning measurement can feel tight by late afternoon, so measure when your feet are at their largest.
- Stand up, with weight on the foot. Your foot lengthens and spreads under load. Place the paper against a wall, stand on it with your heel touching the wall, and have someone mark the tip of your longest toe — which is not always the big toe.
- Measure both feet. A few millimeters of difference between left and right is completely normal. Always size to the longer foot.
- Wear the socks you plan to use. A thick winter sock can easily add a couple of millimeters. If the shoes are for winter, measure with winter socks.
Measure the distance from the wall mark to the toe mark in a straight line. Write down both numbers in centimeters. This pair of numbers — not "I'm usually a 42" — is your real size.
Step 2: Add toe allowance
Here is the part that trips up people coming from conventional shoes. A barefoot shoe should not end where your toes end. Your foot lengthens as it rolls through each step, and your toes need space to splay under load — that splay is a big part of why barefoot shoes feel so stable. The extra space in front of your longest toe is called toe allowance.
A practical target is about 10–12 mm of space beyond your longest toe — roughly the width of a thumb. Somewhat less can work for snug-fitting dress styles; growing kids and long-distance walkers often go a little more. Below 5 mm your toes will start hitting the front on descents; much beyond 15 mm the shoe starts to flop and crease in the wrong places.
So the length you are actually shopping for is:
foot length + toe allowance = internal shoe length.
If your longer foot measures 26.0 cm, you are looking for a shoe with an internal length of roughly 27.0–27.2 cm. That single number lets you shop confidently across any brand that publishes internal lengths — and skip any brand that doesn't.
Step 3: Decode the EU and US systems
Now for the chart itself. European sizes are built on a unit called the Paris point, a French shoemaking convention dating back to the early 1800s. One Paris point is 6.67 mm — exactly two-thirds of a centimeter — and an EU size is simply the length of the last measured in Paris points. Multiply an EU size by 0.667 and you get the theoretical last length in centimeters: an EU 42 corresponds to about 28.0 cm.
US sizes use a different, older unit — the barleycorn, a third of an inch — and a different starting point, with separate scales for men and women. Because the EU step (6.67 mm) and the US step (about 8.46 mm) don't line up, EU-to-US conversions are almost never whole numbers. Every conversion chart you have ever seen is an approximation, which is why the same EU 42 gets labeled US 8.5 by one brand and US 9 by another.
The practical conclusion: use US sizes only as a rough entry point, and make the final decision in centimeters. Here is how the systems roughly relate, using the standard EU sizing math with a 12 mm toe allowance:
| EU size | Theoretical internal length | Fits foot up to* | US women (approx.) | US men (approx.) |
|---|---|---|---|---|
| 37 | 24.7 cm | 23.5 cm | 6.5 | – |
| 38 | 25.3 cm | 24.1 cm | 7.5 | – |
| 39 | 26.0 cm | 24.8 cm | 8 | 6.5 |
| 40 | 26.7 cm | 25.5 cm | 8.5 | 7 |
| 41 | 27.3 cm | 26.1 cm | 9.5 | 8 |
| 42 | 28.0 cm | 26.8 cm | 10 | 8.5 |
| 43 | 28.7 cm | 27.5 cm | – | 9.5 |
| 44 | 29.3 cm | 28.1 cm | – | 10 |
| 45 | 30.0 cm | 28.8 cm | – | 11 |
*Theoretical values from the Paris-point formula, assuming a 12 mm toe allowance. Real internal lengths vary by model and brand — a boot last and a ballet-flat last in the same size are not identical. Always check the specific model's chart when one is published.
Length is only half the story: width and toe box shape
Two feet of identical length can need very different shoes. If your forefoot is wide, or your big toe sits straight rather than angling inward, a narrow tapered shoe will pinch long before the length runs out — and no amount of sizing up fixes a toe box that is the wrong shape. Sizing up for width just gives you a shoe that is too long and still tight across the ball of the foot.
This is exactly the problem a wide toe box solves: the shoe is widest at the toes, where your foot is widest, so you can choose your size purely by length. When you try the shoes on, you should be able to wiggle and splay all five toes freely while the midfoot and heel stay comfortably held. For a deeper look at how the shoe should feel on foot — heel hold, strap tension, break-in — see our full guide on how barefoot shoes should fit.
Five common sizing mistakes
- Ordering your "usual" size without measuring. Your usual size describes other brands' lasts, not your feet.
- Measuring in the morning. Feet are smallest right after you wake up; evening measurements prevent the 3 p.m. squeeze.
- Sizing to the smaller foot. Always fit the longer foot; the other one will never complain about a millimeter of extra room.
- Confusing foot length with internal length. A chart that says "EU 42 = 26.8 cm" usually means the largest foot that size fits, not the inside of the shoe. Read the column headers carefully.
- Treating EU–US conversion as exact. It never is. When a listing shows both, trust the centimeter value behind the EU size.
Frequently asked questions
Should I size up in barefoot shoes?
Not automatically. Barefoot shoes are not "bigger" shoes; they are foot-shaped shoes. Measure your foot, add 10–12 mm, and match that to the brand's chart. Many people do end up a half or full EU size above their conventional size, but that is a result of measuring properly — not a rule to apply blindly.
What if I'm between two sizes?
Go up, not down. Slightly too much toe allowance is a minor cosmetic issue; too little means toes hitting leather on every downhill step. If a style runs snug and you plan to wear thicker socks, the larger size is almost always the right call.
My feet measure two different sizes. Which do I order?
Size to the longer foot. A difference of up to about half a centimeter between feet is common and rarely causes problems — adjustable closures like laces take up the slack on the shorter side.
Is an EU-to-US conversion chart reliable?
Only as a starting point. The two systems use incompatible step sizes, so every conversion involves rounding. If you know your foot length in centimeters, you can ignore the US column entirely and shop by EU size and internal length with far more confidence.
Measure once, shop with confidence
Ten minutes with a pencil and a ruler beats any amount of guesswork. Once you know your foot length in centimeters, every size chart — ours or anyone else's — becomes easy to read: add your toe allowance, find the matching internal length, done. If you are just starting your barefoot journey, our guide on transitioning to barefoot shoes covers what to expect in the first weeks. And when you are ready to put your new number to work, our men's and women's barefoot collections list every style in EU sizes — measured the way this guide assumes.
