Birkenstock to adidas shoe size
The short answer
Birkenstock 40 is adidas 9 or 9.5 by the two brands' own charts.
At least one of the two brands publishes no foot length, so the rows line up the US size both charts print. Treat it as the label conversion, not a fit.
| Birkenstock | Birkenstock builds it for | adidas, by chart | Same label | adidas builds it for | adidas also prints |
|---|---|---|---|---|---|
| 35 | not published | not made | not published | not published | not published |
| 36 | not published | 5 or 5.5 | not published | foot length 22.1 cm | US men's 4 · UK 3.5 · EU 36 · CM / JP 22 |
| 37 | not published | 6 or 6.5 | not published | foot length 22.9 cm | US men's 5 · UK 4.5 · EU 37 1/3 · CM / JP 23 |
| 38 | not published | 7 or 7.5 | not published | foot length 23.8 cm | US men's 6 · UK 5.5 · EU 38 2/3 · CM / JP 24 |
| 39 | not published | 8 or 8.5 | not published | foot length 24.6 cm | US men's 7 · UK 6.5 · EU 40 · CM / JP 25 |
| 40 | not published | 9 or 9.5 | not published | foot length 25.5 cm | US men's 8 · UK 7.5 · EU 41 1/3 · CM / JP 26 |
| 41 | not published | 10 or 10.5 | not published | foot length 26.3 cm | US men's 9 · UK 8.5 · EU 42 2/3 · CM / JP 27 |
| 42 | not published | 11 or 11.5 | not published | foot length 27.1 cm | US men's 10 · UK 9.5 · EU 44 · CM / JP 28 |
| 43 | not published | 12 or 12.5 | not published | foot length 28 cm | US men's 11 · UK 10.5 · EU 45 1/3 · CM / JP 29 |
| 44 | not published | 13 | not published | foot length 28.8 cm | US men's 12 · UK 11.5 · EU 46 2/3 · CM / JP 30 |
| 48 | not published | not made | not published | not published | not published |
What wearers say
Charts describe a garment. People who own both brands describe a fit, and their answer ranks above this table once five of them stand behind it. Pick your size in the converter to see whether there are enough yet.
Sources
- Birkenstock size guide, read on 2026-09-18.
- adidas size guide, read on 2026-09-17. adidas on TrueToSize