Nike vs Adidas Sizing: Which Runs Small, and by How Much
A model-by-model comparison of Nike and Adidas sizing from real fits: which lines run narrow, which run long, and how to pick a size when switching brands.
Nike and Adidas both build on a US size base, both quote the same EU and UK equivalents within half a size, and yet a person who is a solid 10 in one is frequently a 10.5 in the other. The label is not lying; the lasts are different. Nike lasts are narrower through the midfoot and forefoot, Adidas lasts are wider but often shorter in effective length on certain models. Here is how that plays out across the shoes people actually buy.
The short answer
- Nike runs narrow. Length is generally true to the chart, but the forefoot is tight. If your foot is average to wide, you will feel Nike as “small” even when the length is right. Common fix: half size up, or choose a model on a roomier last.
- Adidas runs true to slightly long in most lifestyle models, and the Boost/Ultraboost family runs long enough that many people go half a size down. Adidas Originals in leather (Stan Smith, Superstar) run large.
- Switching Nike to Adidas: keep your size for Adidas performance shoes, go half down for Stan Smith, Superstar and Ultraboost.
- Switching Adidas to Nike: keep your size only if your foot is narrow; otherwise go half up, especially in Air Force 1, Dunk and Pegasus.
Model-by-model comparison
The table uses a 270 mm foot (chart size US men’s 9) as the reference. “Recommended” is what I would order sight unseen for that foot with standard width.
| Model | Chart size | Recommended | Why |
|---|---|---|---|
| Nike Air Force 1 | US 9 | US 8.5–9 | Runs long and boxy; many go down half |
| Nike Dunk Low | US 9 | US 9.5 | Narrow toe box, stiff leather |
| Nike Air Max 90 | US 9 | US 9.5 | Notoriously tight forefoot |
| Nike Air Max 97 | US 9 | US 9.5 | Narrow; hard to break in |
| Nike Pegasus 41 | US 9 | US 9–9.5 | True length, snug midfoot |
| Nike Vomero / Invincible | US 9 | US 9 | Roomier running last |
| Nike Blazer Mid | US 9 | US 9 | True to size, slightly narrow |
| Adidas Stan Smith | US 9 | US 8.5 | Runs long, wide toe |
| Adidas Superstar | US 9 | US 8.5 | Shell toe adds length |
| Adidas Samba OG | US 9 | US 9–9.5 | Runs narrow and tight at first; leather stretches |
| Adidas Gazelle | US 9 | US 9.5 | Narrow suede, stiff heel |
| Adidas Ultraboost | US 9 | US 8.5–9 | Long, stretchy knit upper |
| Adidas Adizero (racing) | US 9 | US 9 | True to size, snug |
| Adidas Forum / Campus 00s | US 9 | US 9 | Roomy, true to size |
Two Adidas models break the “Adidas runs big” rule: Samba and Gazelle. Both are on a narrow, low-volume last and are the shoes I see returned most for being tight. Nike’s Air Force 1 breaks the opposite rule; it is Nike’s roomiest common shoe.
Why the brands differ
Nike’s core lasts were developed around American running feet in the 1970s and remain relatively narrow. The company sells wide fittings only in a handful of running models, so on most lifestyle shoes the only width option is to go up a half size, which adds about 4 mm of length you may not need.
Adidas builds most of its lifestyle line on a broader European last and then rounds its EU-to-US conversion generously. An Adidas US 9 is marked EU 42.67, printed as 42 2/3, while a Nike US 9 is EU 42.5. That third of a Paris point (about 2 mm) is small, but combined with the wider last it is why Adidas feels bigger.
The two brands also measure the printed cm/JP figure differently. Nike’s cm figure is the foot length the shoe is intended for. Adidas’ cm figure historically ran closer to the insole length, which is why an Adidas box may say 27.5 cm for the same US 9 that Nike marks 27 cm. If you are shopping from a cm-based store, ignore the cm on Adidas boxes and use the US number.
Women’s sizing between the two
Both brands use the standard 1.5-size men’s-to-women’s offset (women’s 10.5 = men’s 9), so cross-gender shopping is consistent. The width difference is the issue: Nike women’s shoes are built on a narrower last than the men’s version, whereas many Adidas women’s lifestyle models are simply the men’s last in smaller sizes. Women with average-width feet who find Nike tight can often buy the men’s version of the same Nike model 1.5 sizes down and get more room without changing length. The women’s shoe converter handles that offset.
How to size when switching brands
- Measure your foot in millimeters. If you have not done that recently, this guide takes five minutes.
- Look up your millimeter figure on the men’s or women’s converter to get the chart size.
- Apply the model adjustment from the table above.
- If your forefoot width is over about 103 mm on a 270 mm foot, add a further half size for Nike and consider New Balance’s 2E options instead; New Balance is the only one of the three that treats width as a standard option.
The brand pages at Nike shoe sizes and Adidas shoe sizes hold the full charts including kids and toddler ranges.
Kids’ models
The pattern holds for children. Nike kids’ shoes (Air Force 1 GS, Dunk GS) run narrow, and the GS (grade school) sizes are true to the youth chart. Adidas kids’ Superstar and Stan Smith run long, so a child between sizes should get the smaller one. For toddlers, both brands are roughly equal; use the kids’ shoe converter from a measured foot length rather than age, since a four-year-old can be anywhere from a 9C to a 12C.
FAQ
Should I go half a size up in Nike?
For Dunk, Air Max 90, Air Max 97, Air Max 1 and Pegasus, yes, unless your foot is narrow. For Air Force 1 and most Vomero/Invincible running shoes, stay at your chart size. Nike length is usually right; it is the narrow forefoot that makes people feel they need a bigger shoe.
Do Adidas Sambas run big or small?
Small. Samba, along with Gazelle and Handball Spezial, is on a narrow last and fits tight across the toes on the first few wears. Most people go up half a size. This is the opposite of Stan Smith and Superstar, which run large.
Is a Nike 10 the same as an Adidas 10?
Both are intended for roughly a 280 mm foot, but the Adidas 10 will be about 2 mm longer and noticeably wider. If you are a comfortable 10 in Nike Air Max, you will probably be a 9.5 in Adidas Ultraboost and a 10 in Adidas Samba.