Quick brief
What to know before you calculate
A short read on the assumptions, trade-offs and definitions that shape the answer.
- Measure both feet and use the larger foot as the starting point.
- Foot length narrows the size range, but width, shape and brand fit still matter.
- Children's feet should be measured regularly because growth can be uneven.
Measure in the socks you expect to wear
Place paper on a hard floor, stand naturally, mark the heel and longest toe, then measure the distance in millimetres. Measure while standing because the foot spreads under body weight. Repeat for both feet and start with the larger measurement.
Leave room for movement
Shoes usually need a little space beyond the measured foot length. The right allowance depends on shoe type, age and use. Running shoes often need more room at the front than formal shoes, while children's shoes need space for growth without becoming unstable.
Convert size systems carefully
UK, US and EU systems are not perfectly aligned. A conversion chart can narrow the choice, but brands use different lasts and may publish their own size charts. Use brand guidance when buying a specific model.
Fit beats the label
The printed size is only a starting point. Heel slip, toe pressure, width, arch position and how the shoe bends all affect comfort. If two sizes are close, compare the brand chart, return policy and the type of use before deciding.
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