When it comes to performance footwear, the right fit is everything. From training for a marathon, hitting the gym, or just needing a comfortable pair of everyday sneakers, knowing how adidas and ASICS compare in size can make all the difference, seeing as they're two of the biggest brands you can buy.
This adidas vs ASICS size comparison guide covers length, width, fit tips, and break-in advice so you can confidently choose the perfect pair from these two leading sportswear brands.
How Should adidas and ASICS Shoes Fit?
Comfortably is the ultimate answer, though there's more to it than that...
Comfort, for me, means zero pain, no heel lift, and a bit of space to let my feet breathe, both during daily wear and while training. Fortunately, both adidas and ASICS offer specific recommendations to help you get the best possible fit, especially when it comes to running and performance shoes.
ASICS Fit Guidelines:
- Leave a thumb’s width of space between your longest toe and the front of the shoe.
- For running shoes, ASICS recommends going half a size up from your regular shoe size to avoid pressure and allow room for foot expansion.
adidas Fit Guidelines:
- adidas suggests leaving about half a thumb’s width at the toe.
- The heel should feel secure, with a snug fit around the heel and midfoot. This is especially important for running or training shoes to avoid slippage.
General Width Tip:
The widest part of your foot should align with the shoe’s widest section, allowing enough space without squeezing.
A general rule of thumb from Clarks is that the ball area and metatarsal bone should fit comfortably within the shoe's widest section. This will prevent any inward compression of your foot and allow enough space to accommodate its width.
adidas vs ASICS Length Differences
adidas shoes tend to run smaller in length than ASICS, but the sizing labels can be confusing, especially in UK sizes.
For example:
- A UK 8 adidas is shorter than a UK 7.5 ASICS.
- A UK 8 ASICS can be over 1 cm longer than a UK 8 adidas.
Tip: Always use the centimeter measurement on the brand’s sizing chart rather than relying on US or UK size labels alone.
adidas vs ASICS Width Comparison
Both brands offer different width options, but neither publishes exact centimeter widths in their official charts.
However, this information can be found online. Here is a breakdown of the codes for a Men's US 8 shoe:
- B (Narrow): ~8.73 cm
- D (Standard): ~9.68 cm
- 2E (Wide): ~10.64 cm
- 4E (Extra Wide): ~11.59 cm
Remember, widths increase with shoe size, so a US 12 “D” will be wider than a US 8 “D”, for example. Bear this in mind when browsing different shoe widths.
Which Brand Should You Choose Based on Fit?
- Choose adidas if you prefer a snug, locked-in feel, especially around the heel and midfoot.
- Choose ASICS if you want extra space in the toe box or plan to run long distances.
If you’re between sizes:
- adidas: Go half a size up for comfort.
- ASICS: Their fit already offers more space, but half a size up may help for high-mileage runs.
Do You Need to Break in adidas and ASICS Shoes
Yes, both brands often require a short break-in period for optimal comfort.
- adidas Ultraboost, Adizero, and similar models may feel snug initially due to sock-like fits and responsive midsoles. After 10–15 miles, the materials soften and mold to your feet.
- ASICS Gel-Nimbus and Gel-Kayano can feel firm at first because of their structured support and gel cushioning. Expect them to loosen up after 2–3 runs or walks.
Break-in tip: Wear your new shoes around the house or on short walks before long runs to help materials adapt.
Final Thoughts
Finding the right size in adidas vs ASICS sneakers comes down to understanding their subtle differences in length and width. Always measure your feet in centimeters and compare them to the brand’s chart before buying, especially if you shop online.
A proper fit not only boosts comfort but also supports performance, prevents injuries, and keeps your feet happy all day.