The #1 Rule: Running Shoes Should Be Bigger
Your running shoe should be half a size to one full size larger than your casual shoe. Here's why:
- Foot swelling — feet expand 3-8% during a run
- Toe splay — toes spread on impact and need room
- Downhill protection — prevents black toenails from toes hitting the front
Rule of thumb: There should be a thumb's width (~10mm) between your longest toe and the front of the shoe.
Running Shoe Size Comparison (27.0 cm Foot)
| Brand | US Size | EU Size | Fit Notes |
|---|---|---|---|
| Nike | US 9 | EU 42.5 | Standard fit, some models narrow in toe box |
| Hoka | US 9 | EU 42.7 | Wide toe box, narrow heel in most models |
| Brooks | US 9 | EU 42.5 | True to size, wide options available |
| ASICS | US 9 | EU 42.5 | True to size, Gel-Kayano wider than Nimbus |
| New Balance | US 9.5 | EU 43 | Best wide options (2E, 4E, 6E available) |
| Saucony | US 9 | EU 42.5 | True to size, wide options available in many models |
| On Running | US 9 | EU 42.5 | Swiss fit, may run 0.5 narrow — try Cloud 5 for wider feet |
| Salomon | US 9 | EU 42.7 | European fit, runs 0.5 narrow |
Get Your Running Size
Enter your foot measurement and see your exact running shoe size across all brands.
Find My Running Size →How to Size Running Shoes Correctly
- Measure your feet in the evening — they're at their largest after a day of activity.
- Wear your running socks while trying on shoes.
- Add 5-10mm to your measurement — this is the "running room."
- Measure both feet — always use the larger one.
- Test on a run, not a walk — a shoe that fits standing may not fit running.
When to Replace Running Shoes
Running shoes lose cushioning after 500-800 km (300-500 miles). Signs it's time:
- Outsole is worn smooth
- Midsole creases don't bounce back
- New aches or pains after runs
- Shoe feels "flat" or less bouncy