What size should your running shoes be?

Why you don't run in your everyday size

When you run, your feet swell (especially after an hour or in hot weather) and slide forward with every stride, even more on downhills. A shoe in your exact everyday size ends up squeezing your toes: blisters, black toenails, pain under the forefoot.

Simple rule: keep a thumb's width (about 1 cm) between your longest toe and the tip of the shoe. In practice, that often means half a size to a full size above your everyday size.

Measuring your foot properly

1. Measure at the end of the day, when your feet are at their largest.
2. Stand on a sheet of paper, heel against a wall, wearing your running socks.
3. Mark your longest toe, measure the distance to the wall, then repeat with the other foot: always go by the larger one.
4. Add about 1 cm to get the ideal inner length.

EU, UK, US: watch the conversions

Size charts vary from one brand to another, and US men's and women's sizes are not the same. To compare from your foot length, Runometry's running shoe size chart lists the conversions by brand.

Width matters as much as length

A foot squeezed at the sides causes hot spots even at the right length. If your forefoot spills over the insole when you stand on it, look for a wide model (often labelled "wide" or "2E").

Trail and long distances

On a trail with long descents or an ultra, feet swell even more: favour the top of the range (a full size up) and a lacing that locks the heel.

Test before race day

Never race in brand-new shoes. Do at least three or four runs, including a long one, before the big day. Found the right pair? Now pick your next race.