Birkenstock Blue Footbed Sizing: Making Sense of 56 EU Size and Width Variants

Birkenstock builds its sizing around EU numbers, and this listing follows suit. Most of the 56 labels lead with the EU size and then translate it, like "38 M EU / US Women 7-7.5" or "45 M EU / US Men 12-12.5". Each label is its own child ASIN on Amazon (those two are B001HY0HPQ and B001HY44IW respectively), which is part of why the variant list runs so long.

EU sizing is unisex, so a single EU number covers both a US women's range and a US men's range. That is why many labels carry two conversions at once. If you know your US size, scan for it in the back half of the label instead of trying to convert to EU in your head. The US range printed on the label is the one Amazon will use to describe what arrives.

Multiply those EU sizes by width and you get most of the way to 56. Many EU sizes appear more than once, up to three times, one per width letter: N for narrow, M for medium or regular, and W for wide. Size 41 is a good example. The listing offers "41 N EU / US Men 8-8.5 / US Women 10-10.5 N", a plain "41 M EU", and "41 W EU / 10-10.5 C/D US Women / 8-8.5 2E US Men".

Notice how the wide label spells out US letter widths, C/D for women and 2E for men. If you normally buy wide shoes in US sizing, that is your signal to look for the W variant of your size. As a general rule, width is worth getting right on any shaped footbed, because the shaping sits under specific parts of your foot. On a flat foam insole a little extra width rarely matters. On a shaped one, it changes where everything lands.

Not every label follows the pattern. A few are bare numbers, like "35", "42", and "46", with no width letter and no US conversion in the label itself. Two are stranger still: "Medium (Pack of 1)" points to ASIN B002Y4ESVC, and "M14-14.5" points to B002Y4ET48. These looked like errors to us at first. They are not. They are simply variants with inconsistent naming, and they are just as buyable as the tidy ones.

Rather than making you guess, we recorded all 56 labels along with the exact child ASIN behind each one. Our catalog entry for the Blue Footbed lists every label and its ASIN, so you can open your size and width directly instead of hunting through Amazon's size picker and hoping the dropdown behaves.

The listing also carries color variants: Blue (Sport), Clear, Blue, and Multi. Here is the quirk we most want you to know about. If you select a size and color combination that is not available, Amazon can silently switch you to a different color rather than telling you the combination is out of stock. You pick Clear in your size, and the cart quietly holds Blue. When we built our size map, we recorded the ASIN the address bar actually showed after each click, not the one we intended to reach, precisely because of this behavior. We suggest you do the same: after selecting your size, glance at the color name and the ASIN in the URL before you add to cart.

A few housekeeping notes from our July 16, 2026 check. The seller on the verified listing was a third party called DLD Square, with the order shipping from Amazon. A separate boxed listing (B0DT2H6D1C) was showing "Currently unavailable" when we looked. Amazon listings shift constantly, and variant-heavy ones shift more than most, so before you buy, confirm your size label, the current price, and availability on the Amazon page itself.

If 56 options still feels like too many, that is exactly what our questionnaire is for. Answer a few quick questions about your shoe size, your width, and the shoes you plan to wear insoles in, and our two-minute match questionnaire will point you to the options in our catalog that line up with your answers, this footbed included when it makes sense. Prefer to compare everything yourself? Browse the full catalog and jump straight to the Blue Footbed's complete 56-label size map from there.