Do ASICS Shoes Run Big or Small? (Data from 844 Pairs)

Short answer: ASICS shoes are close to true to size for most people, but they trend a touch on the small and snug side, especially the performance running line. Feetlot data across 844 verified pairs spanning 34 ASICS models confirms the pattern: most ASICS models come up a little smaller than the reference shoe, so a half size up is the safe call for running, while older court and walking styles sit closer to true to size. The big catch with ASICS is consistency, which is low, so the right move really does depend on the exact model.

What the Feetlot Data Says About ASICS Sizing

Based on 844 verified pairs across 34 ASICS models in the Feetlot database, ASICS lands just on the snug side of true to size. The central tendency is a small but clear lean toward running smaller than the Nike Air Force 1, the reference shoe Feetlot uses as its baseline. In plain terms, the typical ASICS model comes up around a third of a size smaller than that baseline, which is why so many runners end up reaching for a half size up.

The more useful finding, and the one no generic size chart can give you, is consistency, and here ASICS scores low. Sizing varies a lot from one model to the next in the Feetlot data. The running flagships pull noticeably small, while several older court, trail, and walking models sit close to true. That spread is wide enough that a single brand-wide rule will mislead you on at least some shoes. The honest takeaway: treat ASICS as a brand where you check the specific model rather than trusting one blanket number, and the sections below break down exactly which way each popular model leans.

Which ASICS Shoes Run Big, and Which Run Small

The clearest split in the Feetlot data is by category. ASICS performance running shoes run the smallest, while the brand's older court, trail, and walking models run closer to true or even slightly roomy. If you only remember one thing: size up for the Gel running line, stay true for the casual and court styles.

ASICS models that run small (size up about a half size)

The running cushioning models are the snuggest in the entire ASICS range. The GEL-Cumulus 14 runs the smallest of the group and is a clear half size up. The premium cushioning line behaves the same way: the Gel-Nimbus 22, the older GEL-Nimbus 14, and the even earlier GEL-Nimbus 13 all come up small enough that most owners size up. The stability flagship GEL-Kayano 18 and the popular daily trainer GT-2170 both run small as well, and they are two of the most-owned ASICS shoes in the Feetlot database, so this is a well-supported call. The lightweight racing-leaning GEL-Rebel and the retro lifestyle Gel-Lyte V round out the size-up group.

ASICS models that run closer to true (size down or stay put)

On the other side, ASICS court, trail, and walking models run noticeably roomier relative to the rest of the brand. The retro court shoe Ultimate 81 runs the largest of the bunch and is the one model where many owners take their normal size or even consider going down. The indoor court GEL-Rocket 6, the throwback Gel-Kayano 5, the trail-oriented GEL-Kahana 5, the classic Gel 1090, and the walking-focused GEL-Quickwalk all sit closer to true to size than the running flagships. For these, your standard size is usually the right starting point.

The popular middle

A few high-volume models sit between the extremes. The retro Gel-Lyte III is one of the most-owned ASICS shoes in the Feetlot data and runs only slightly small, so it is close to true with a snug-leaning fit. When in doubt on a lifestyle ASICS, true to size with thin socks is a reasonable default.

How to Find Your ASICS Size

Because ASICS consistency is low, the smartest approach is to size by category and by foot shape rather than by a single rule.

Performance running (Gel-Nimbus, Gel-Kayano, GT, Gel-Cumulus): Size up a half size from your everyday sneaker size. Feet swell on long runs, and these models already run snug, so the extra room pays off.
Court, trail, and walking models: Start at your true size. These run roomier in the Feetlot data, and only a few people need to go down.
Lifestyle and retro (Gel-Lyte line): True to size for most, snug for some. If you like a roomy casual fit, half up is fine.
Wide feet: ASICS is one of the better mainstream brands for width because many performance models come in 2E and 4E widths. Choose the wide variant before sizing up, since going up a full size to chase width distorts the length.
Narrow feet: The snug running line can actually work in your favor. Stay true and lace with a heel-lock to lock the midfoot.
Measure first: Measure both feet in the evening, in centimeters, and match to the ASICS chart below. ASICS publishes precise centimeter lengths, which makes its chart more reliable than most when you measure accurately.

ASICS vs Other Brands

Against the major brands, ASICS sits in the middle of the sizing spectrum and is generally well behaved on length. Compared with Nike, ASICS tends to run a little smaller and snugger, so people who take their true size in Nike running shoes often add a half size in the ASICS Gel line. Compared with New Balance, the two are similar in length, but ASICS offers comparably strong width options, so wide-footed runners can cross-shop them on equal footing. Adidas running shoes, by contrast, often feel longer and narrower, so an ASICS at the same labeled size usually fits shorter and a touch wider. Against Brooks, the other running specialist, ASICS and Brooks both run slightly snug and reward a half size up in their cushioning models. The practical summary: if your reference is a casual sneaker, ASICS will feel a half size smaller; if your reference is another running brand, ASICS is in the same neighborhood but on the snug end.

ASICS Size Chart (US / UK / EU)

Standard ASICS men's conversion. Measure your foot length in centimeters and match to the nearest size, rounding up if you are between sizes.

US (Men)	UK	EU	Foot length (cm)
6	5	39	24.0
6.5	5.5	40	24.5
7	6	40.5	25.0
7.5	6.5	41.5	25.5
8	7	42	26.0
8.5	7.5	42.5	26.5
9	8	43	27.0
9.5	8.5	44	27.5
10	9	44.5	28.0
10.5	9.5	45	28.5
11	10	46	29.0
11.5	10.5	46.5	29.5
12	11	47	30.0
13	12	48	31.0

For ASICS women's sizing, subtract roughly 1.5 from the US men's number. EU and centimeter values stay the same for a given foot length.

How Feetlot Measures This

Feetlot fits a global offset model to more than 100,000 verified owner-reported shoe records. Each shoe gets a single number that captures how it drifts in fit from the reference shoe, the Nike Air Force 1. Aggregating those numbers across every model in a brand reveals the brand's overall pattern, how consistent it is, and exactly which models break from it, which is how the ASICS running-versus-court split above surfaced from the data rather than from opinion. The result is a verdict grounded in what people actually own and wear, not in a manufacturer chart. To get a personal recommendation in any specific ASICS model, sign in and add the shoes you already own, and Feetlot will translate your real fits into a predicted size for the model you are eyeing.

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Frequently asked questions

Do ASICS shoes run big or small? ▾

ASICS shoes run slightly small overall. Feetlot data across 844 verified pairs from 34 models shows the typical ASICS model comes up a touch smaller than the reference shoe, with the performance running line being the snuggest. Court and walking models run closer to true.

Is ASICS true to size? ▾

ASICS is close to true to size but leans snug, especially in its Gel running models. Many runners find a half size up more comfortable, while casual and court models fit true. Because ASICS sizing varies a lot by model, checking the specific shoe matters more than with most brands.

Should I size up or down in ASICS? ▾

Size up a half size for ASICS performance running shoes like the Gel-Nimbus, Gel-Kayano, GT, and Gel-Cumulus lines, since they run small and your feet swell on runs. Stay true to size for court, trail, walking, and most lifestyle models, which fit roomier in the Feetlot data.

Which ASICS shoes run small? ▾

The running models run smallest. In the Feetlot data, the GEL-Cumulus 14, Gel-Nimbus 22, GEL-Nimbus 14, GEL-Nimbus 13, GEL-Kayano 18, GT-2170, and GEL-Rebel all come up small enough that most owners size up a half size.

Which ASICS shoes run big or true to size? ▾

The older court, trail, and walking models run roomier. The Ultimate 81 runs the largest, and the GEL-Rocket 6, Gel-Kayano 5, GEL-Kahana 5, Gel 1090, and GEL-Quickwalk all sit close to true, so your normal size is the right starting point for these.

Do ASICS Gel-Nimbus shoes run small? ▾

Yes. The Gel-Nimbus line is among the snuggest ASICS models in the Feetlot data, including the Gel-Nimbus 22, GEL-Nimbus 14, and GEL-Nimbus 13. A half size up is the common recommendation, with room for swelling on long runs.

Does the ASICS Gel-Kayano run true to size? ▾

The GEL-Kayano 18 runs slightly small in the Feetlot data and is one of the most-owned ASICS models, so the size-up call is well supported. Most runners go a half size up from their everyday sneaker size for a comfortable long-run fit.

Are ASICS good for wide feet? ▾

Yes. ASICS is one of the better mainstream brands for width because many performance models offer 2E and 4E widths. Choose the wide variant rather than sizing up a full size to chase room, since going up too far distorts the length.

How does ASICS sizing compare to Nike? ▾

ASICS tends to run a little smaller and snugger than Nike. People who take their true size in Nike often add a half size in the ASICS Gel running line. Against other running brands like Brooks and New Balance, ASICS is similar in length but on the snug end.

How does Feetlot know how ASICS shoes fit? ▾

Feetlot fits an offset model to more than 100,000 verified owner-reported shoe records, giving each model a number for how it drifts from a reference shoe. Aggregating across ASICS models reveals the brand pattern and the model exceptions, based on what people actually own rather than manufacturer charts.