Why Your Size Changes Between Brands
A UK 9 is not a UK 9. Sizing conventions differ by brand and by model line, which is why buying online without trying is a gamble.
In short
- There is no enforced international standard for shoe sizing, so brands differ legitimately.
- Width and volume vary more between brands than length does, and matter more for comfort.
- Model lines within one brand can fit differently from each other.
- Measure your feet in centimetres — that is the one number that transfers.
People assume their size is a fixed property of their feet. It is a property of a particular brand’s last — the foot-shaped form a shoe is built around — and lasts differ between companies and between model lines at the same company.
Why there is no standard
Shoe sizing systems grew up regionally and were never unified into an enforced standard. UK, US, EU and Japanese systems all measure differently, conversion charts disagree with each other, and nothing obliges a manufacturer to match a competitor. A brand can change its own sizing between generations of a model and break no rule.
Width and volume matter more than length
Most fit complaints described as “too small” are actually width or volume problems. Two shoes of identical length can feel completely different depending on how much room there is across the forefoot and over the instep.
Some brands run generally narrow, others generally roomy, and a few offer genuine width options rather than just a longer shoe. If your feet are wide, looking for a brand that publishes actual widths will do more for you than sizing up.
The number that transfers
Measure your feet in centimetres, at the end of the day, standing, both feet. Feet are commonly different sizes — fit the larger one.
Many brands publish a centimetre or “mondopoint” measurement in their size charts, which is the only figure that compares meaningfully across brands. Use your measurement against each brand’s own chart rather than assuming your familiar number.
Buying online
Buy from somewhere that accepts returns on shoes worn indoors, and try them on carpet before committing. If you are replacing an identical model you already own and the version has not changed, you are reasonably safe. If the version number has moved, treat it as a new shoe — brands revise lasts between generations without announcing it prominently.