Shoe size by manufacturer: why your size 10 isn't the same brand to brand

Two shoes labelled “US 10” from different brands can differ by 5-10 mm in actual interior length, plus differences in width, toe-box height, and arch placement. The shoe sizing system measures thelast (the wooden form the shoe is built on), not the foot, and every manufacturer has their own last geometry. This guide explains what to expect from the most common brands.

Why brands disagree

Three sources of variation:

1. Last geometry. The wooden or digitally-modelled form the shoe is constructed around. Width, instep height, toe-box volume, and heel-to-ball ratio all vary. Two shoes built on different lasts at the same nominal size feel different.
2. Construction allowances. A goodyear-welt dress shoe has a stiff structure that holds the last shape rigidly. A running shoe with knit upper stretches with use; brands account for this differently.
3. Geography.European dress brands tend to run narrow. American athletic brands target a wider average foot. Japanese brands cater to typically narrower feet still. Even within US brands, “D” width standards aren’t quite the same.

The brands, roughly catalogued

Athletic — typically run true or slightly small

• Nike. Generally true to size for casual; running models often run a half-size small with a narrow last. The Pegasus, Vaporfly, and Alphafly all skew narrow.
• Adidas. True to size in lifestyle (Stan Smith, Samba) and slightly large in running (Ultraboost, Adios).
• New Balance. True to size, often with width options (D, 2E, 4E). The best mass-market option for wide feet.
• Asics. True to size in the GT and Cumulus; slightly narrow in the Gel-Kayano.
• Brooks. Slightly large; many runners size down half. Wide-width versions widely available.
• Hoka. True to size in most models; Clifton and Bondi run wide-ish for high-volume feet.
• On. Slightly small and narrow; many size up half.

Dress shoes — varies wildly

• Allen Edmonds (US). Generally a half-size larger than athletic shoes. The Park Avenue at “10D” fits like a Nike 10.5D.
• Alden (US). Built on multiple lasts (Plaza, Barrie, Aberdeen, etc.) that fit very differently. The Barrie last runs about a half-size large with a wide toe box.
• Crockett & Jones (UK). True to UK sizing, which runs about a half-size smaller than US. UK 9.5 fits a US 10 foot.
• Edward Green (UK). Multiple lasts; the 202 fits half a size large with extra toe room, the 82 is narrower.
• Salvatore Ferragamo (IT). Italian sizing runs narrow; many US buyers go a half to full size up.
• John Lobb (UK). Bespoke or high-end ready-to-wear; sizing varies per last, fit is closer than off-the-shelf.

Boots

• Red Wing. Heritage boots (Iron Ranger, 875) typically run a half-size large because they’re built on an old wide last.
• Wolverine 1000 Mile. Similar — half-size large, narrow last.
• Dr. Martens. Notoriously inconsistent. Many buyers size down a full size; women’s buyers often pick men’s sizes for better-fitting toe boxes.
• Blundstone. Australian sizing runs a half-size larger than UK; AU 8 = UK 7.5 = US 9 (men’s).

How to actually buy across brands

1. Measure your foot in millimetres. Heel to longest toe, weight on the foot, end of day (feet are longest in the evening). Both feet — the larger one governs.
2. Find the brand’s own size chart.Most reputable brands publish foot-length-to-size tables. Use the brand’s chart, not a generic conversion.
3. Read width carefully.US D is medium for men; US B is medium for women. 2E is wide; 4E is extra wide; B (men) is narrow. UK and EU sizing don’t encode width as numerically; you may need to specifically ask.
4. Check return policy before buying online.Zappos, REI, Allen Edmonds (1 year), and Nordstrom all have generous return policies that make experimental cross-brand sizing painless. Brand DTC sites vary.
5. Visit a Brannock-equipped store at least once. The Brannock device measures length, width, and heel-to-ball — a baseline that lets you interpret brand-specific charts intelligently.

The cross-region cheat sheet

Standardised conversions to use as a starting point (always check brand chart for the final pick):

Use our shoe size converter for any direction, or the US vs EU shoe size comparison for the full history of how the systems diverged.

Worked example: cross-shopping a running shoe

You wear a New Balance 1080 in US 10.5 D and want to try the On Cloudmonster. New Balance publishes 10.5 D = 285 mm (Mondopoint). On’s own size chart lists US 10.5 = 280 mm — already 5 mm shorter at the same nominal size. Combine that with On’s narrow last and reviewer consensus to size up half (community Fuelly-equivalent for shoes, Reddit r/RunningShoeGeeks). You order US 11 D, which gives you 285 mm interior length — back to your actual foot. The same rule of thumb fails for Brooks Ghost (slightly large, hold US 10.5) and Hoka Bondi (true to size, hold US 10.5). One sizing rule never generalises across brands — always cross-reference the brand’s mm chart, not the US label.

Common mistakes

• Measuring once and trusting it forever.Adult feet grow ~1 mm per decade after age 30 and another full size during a single pregnancy. Re-measure every 2-3 years and any time you notice the same shoe model fitting differently.
• Sizing to the shorter foot.Most people have a 3-8 mm asymmetry between feet. Always fit the longer foot; the shorter foot tolerates a millimetre of slack but the longer foot can’t tolerate a cramped toe box without nail damage.
• Trusting “true to size” reviews uncritically.Reviewers’ baseline brand differs. “True to size” from a Hoka habitué means something different than “true to size” from a Nike runner — they’re calibrated against different lasts. Cross-reference at least three sources.
• Ignoring width.A US 10 D and US 10 2E differ by ~6 mm at the ball of the foot. Buying length-only for a wide foot guarantees rubbing at the metatarsal heads even at “correct” length.
• Measuring in the morning. Feet are 3-5% longer at the end of the day (gravity + activity). The APMA recommends fitting in the late afternoon to match real wearing conditions.

Edge cases

• Diabetic or neuropathic feet.Reduced sensation means you can’t feel a too-tight shoe until tissue damage occurs. Get fitted with a Brannock by a certified pedorthist; size up half if in doubt.
• Orthotic inserts. Aftermarket orthotics take up 3-5 mm of internal volume. Either size up half or buy a model with a removable factory insole that you replace one-for-one.
• Boots over thick socks.Winter boots fitted over a single-pair-of-thick-merino size run a full size larger than the same wearer’s summer trainer size. Bring the socks you’ll wear to the fitting.
• Children’s feet.Children grow 1-2 sizes per year up to about age 12. Re-measure every 3-4 months; never hand down shoes that have moulded to another child’s gait pattern.

For the historical background on why US, EU, and UK diverged, see US vs EU shoe size. Sources: ISO 9407 (Mondopoint); EN 13402-3; Allen Edmonds last specifications (publicly available); Brannock Device documentation; APMA fit guidance.