Should running shoes be bigger than normal shoes?

Yes, most experts recommend going half a size up from your regular shoe size for running shoes. Your feet swell during running and you need space to prevent black toenails.

How do I measure my foot length?

Stand on a piece of paper, mark the heel and longest toe, then measure the distance in centimetres. Measure both feet and use the longer measurement.

Do UK and US shoe sizes differ?

Yes. US men sizes are typically 1 size larger than UK (UK 9 = US 10). US women sizes are typically 2 sizes larger (UK 6 = US 8).

Do shoe sizes vary between brands?

Yes, there can be significant variation between brands. Always try before buying, or check brand-specific size guides alongside these general conversions.

RunCalcs

Shoe Size Calculator — Running Shoe Size Converter

Convert running shoe sizes between UK, US and EU systems.

Foot Length

Sex

How We Calculate This

Shoe Size Conversion

Shoe sizes are calculated from foot length in centimetres:

UK Size = (Foot Length cm - 21.5) / 0.847

US Men = UK + 1 | US Women = UK + 2

EU = UK + 33 (approximately)

For running, we recommend adding 0.5 to your standard UK size to allow for foot swelling during exercise.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always consult a coach or medical professional for personalised training advice.