Adidas adult running shoes use EU sizes in thirds, not whole-and-half sizes, and US fit follows heel-to-toe length in centimeters. EU third sizes are EU sizes split into three steps per whole number, such as 42, 42 2/3, and 43 1/3. For runners, this means a small length change can shift the best US choice. Matching centimeters first prevents tight toes and heel slip on longer runs.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- What are EU third sizes?
- How do EU thirds translate to US fit?
- How do you match your foot length?
- Do women's sizes and models change the choice?
What are EU third sizes?
Adidas lists adult EU footwear sizes in thirds, running 36, 36 2/3, 37 1/3, 38, 38 2/3, 39 1/3, 40 and continuing to large sizes, according to the Adidas men's shoes size chart. Runners should look for the fraction, not assume a half size exists.
Each EU third equals a small foot-length step. Adidas chart increments run about 4–5 mm, for example 25.9 cm to 26.3 cm to 26.7 cm across successive thirds.
How do EU thirds translate to US fit?
A central men's conversion is US 9 equals UK 8.5 equals EU 42 2/3 equals 26.3 cm heel-to-toe, while EU 42 equals US 8.5 and 25.9 cm and EU 43 1/3 equals US 9.5 and 26.7 cm, as shown in Tennis-Point and Running-Point Adidas footwear size tables in the Adidas footwear size tables. One EU third moves the foot-length target by only millimeters.
That small step matters between sizes. A 26.3-cm foot matches US 9, while 26.7 cm matches US 9.5.
How do you match your foot length?
Adidas treats heel-to-toe length in centimeters and inches as the controlling measurement and publishes it alongside every US, UK, and EU equivalent, so shoppers should match foot length first, according to Sizely compiling the official Adidas guide in the Adidas Shoe Size Chart. Start from centimeters, then read across to US size. Sizely describes correct measurement as standing barefoot on paper, marking heel to longest toe, measuring the line, preferably in the afternoon, then converting that centimeter value to Adidas size.
- Stand barefoot on paper with full weight.
- Mark the back of the heel and tip of the longest toe.
- Measure the line in centimeters, preferably in the afternoon.
- Convert that number to Adidas size before checking US fit.
Do women's sizes and models change the choice?
For the same foot length, Stadium Goods sizing charts show Adidas women's US sizes run about one full size above men's US sizes. For example, men's US 4 corresponds to women's US 5 at 22.1 cm. Model cut also changes feel.
Zappos reports Adidas Ultraboost 5x running shoes fit true to size for most wearers, but shoppers with wide feet or between sizes should consider going one-half US size up, in the Women's Adidas Ultraboost 5x product page. Fit varies by running model. Adidas answers and blog reporting via Answers.org notes race models such as Adios Pro 4 run tight in the toe and performance Ultraboost fits tighter than casual NMD. Between-size runners should take the next EU third or half-size up.