How to Buy Sneakers Online Without Getting the Size Wrong

8 min read · Buying guides

Online sneaker shopping has one major downside: you can't try them on. And because shoe sizing is inconsistent across brands, ordering the "same size as always" doesn't guarantee the same fit. Every return, every disappointed unboxing, every pair that gets sold on because they didn't fit — almost all of it comes back to a size mismatch that was preventable.

Here's a practical framework for buying sneakers online and getting the size right the first time.

Step 1: Know Your Foot Length in CM

The most important number you can know when buying sneakers online is not your US size — it's your foot length in centimetres. Your foot length in CM is brand-neutral. It doesn't change between men's and women's systems. It converts cleanly into every other sizing system. And every brand publishes a size chart that maps foot length to their sizes.

To measure: stand on a piece of paper on a hard floor, trace around your foot with a pencil held vertically, and measure from the back of your heel to the tip of your longest toe. Do both feet. Use the larger measurement. That number in CM is your actual foot size.

Common foot lengths and their US equivalents:

25 cm → US Men's 7 / Women's 8.5
26 cm → US Men's 8 / Women's 9.5
27 cm → US Men's 9 / Women's 10.5
28 cm → US Men's 10 / Women's 11.5
29 cm → US Men's 11 / Women's 12.5

Step 2: Check the Brand's Own Size Chart — Not a Generic One

Once you have your foot length, go to the specific brand's website and look up their size chart before ordering. Don't rely on the US size you normally wear. Don't assume that because a Nike fits at US 10, an Adidas will too.

Brands that run small in at least one key model include Adidas (Ultraboost, NMD, Yeezy 350 V2), New Balance in narrow lasts (990, 997) and Converse across the board. Brands that tend to run large include Vans (canvas styles), Converse and some Nike lifestyle models. Brands that are reliably true to size include Nike (most performance and lifestyle shoes), New Balance (most running styles), Jordan (Jordan 1, Jordan 3, Jordan 4) and Puma.

Step 3: Read Reviews Specifically for Sizing Comments

Customer reviews are one of the best sources of real-world sizing information — more useful, in many cases, than the brand's own chart. Look for comments that mention sizing explicitly: "I ordered my usual size and it was too small," "size up half," "fits true to size for me," "runs narrow."

Filter reviews by "most helpful" rather than most recent to surface comments from people who bought the shoe some time ago and have had a chance to assess the fit over multiple wears. Reviews from a single wear session are less informative because many shoes feel different once they've been broken in slightly.

On resale platforms like StockX or GOAT, you'll sometimes find reviewer commentary in the product page or associated blog content. Nike's own website shows verified purchaser reviews that include helpful fit notes. Zappos is excellent for this — they include a "fit" rating and detailed customer size comparisons on most products.

Step 4: Handle Half Sizes Deliberately

If your foot length puts you between two sizes, the general rule is to size up — particularly for closed-toe shoes. Shoes can be laced tighter or padded with insoles, but a shoe that's too small just causes problems.

The exception is shoes that run large or have a wide toe box (Vans, Converse, Air Force 1). In those cases, sizing down to the smaller half size often produces a better fit than sizing up. If the shoe runs large and you go up, you'll have too much room and the shoe will feel sloppy.

For athletic or performance shoes worn for distance running, always size up half a size regardless of where your foot length lands. Feet swell during exercise, and a comfortable fit at rest can become an uncomfortably tight fit after 10km.

Step 5: Check the Return Policy Before You Buy

Even with the best preparation, you'll sometimes get the size wrong. Knowing the return policy before you buy removes the anxiety from the process and means a wrong-size order is an inconvenience rather than a financial loss.

What to look for:

Free returns: Nike.com, Adidas.com, Zappos and most major retailers offer free return shipping. Size-related returns are almost always accepted.
Return window: Most retailers allow 30 days; some (Zappos, some Adidas promotions) offer longer. Keep shoes in their box and try them on inside before wearing outside.
Resale platforms: StockX and GOAT do not accept returns for buyer's remorse. Authentication platforms like these finalise sales once delivery is confirmed. Buy from these platforms only when you're confident in your size.
International orders: Return shipping from international retailers can be expensive. If you're buying from a foreign site, confirm the return logistics and cost before ordering.

Step 6: If You're Buying From a Non-US Site

Shopping on a European, Japanese or Korean sneaker site introduces an extra sizing layer. Never assume the number listed is in the same system you're used to. A European site will list in EU. A Korean platform will list in KR (millimetres). A Japanese site will list in CM.

Always convert through your foot length rather than through a size-to-size shortcut. If you know you're a 28cm foot, you know you need EU 44, KR 280 and JP 28.0 — without any risk of the conversion going wrong.

Convert any size between US, UK, EU, CM and Korean sizing instantly — for men's, women's and kids'. Also includes a foot length calculator to find your exact size.

Use the size converter →

Quick Brand Sizing Reference

Nike: True to size across most styles. Air Force 1 runs slightly wide. Jordan 11 — half size up.
Adidas: Ultraboost, NMD, Yeezy 350 V2 — half size up. Stan Smith, Samba, Gazelle — true to size but narrow.
Converse: Size down 1 full size (men's) or 1.5–2 sizes (women's).
Vans: Half size down. Canvas styles stretch with wear.
New Balance: Generally true to size. Available in width fittings (D, 2E, 4E) which makes them particularly useful for wide-foot buyers.
Puma: True to size across most styles.
Reebok: True to size in Classic Leather and Club C. Some performance styles run slightly small.

Disclaimer: Sizing information is a guide and reflects general consensus. Individual models and production runs may vary. Always verify against the brand's own size chart before purchasing.