Shopping for shoes online is a gamble even when you know your own size — and it gets far harder when you're buying for someone else. A US 9 is a UK 8.5 is roughly a 27 cm foot, and brands routinely vary another half-size on top of that. Here's the full breakdown.

Women's Shoe Sizes

US UK EU CM
5 2.5 35 22
6 3.5 36 23
7 4.5 37 24
8 5.5 38.5 25
9 6.5 40 26
10 7.5 41 27
11 8.5 42 28

Men's Shoe Sizes

US UK EU CM
6 5.5 39 24
7 6 40 25
8 7 41 26
9 8 42 27
10 9 43 27.5
11 10 44 28.5
12 11 45 29.5
13 12 46 30.5

Kids' Shoe Sizes

US UK EU Age (approx.)
4 (Toddler) 3 19–20 1y
7 (Toddler) 6 23–24 2y
10 (Toddler) 9 27 4y
13 (Toddler) 12 31 6–7y
1 (Youth) 13.5 32–33 7–8y
4 (Youth) 3.5 36 9–10y

Children's feet grow quickly — re-measure every 3–4 months for kids under 8.

The Most Reliable Method: Measure in Centimetres

Size labels vary by brand far more for shoes than for clothing — a "size 9" running shoe can fit completely differently from a "size 9" dress shoe. The most reliable approach is to measure actual foot length in centimetres (heel to longest toe, standing, at the end of the day when feet are slightly swollen) and compare that against the brand's specific size chart, not just the generic conversion table.

Don't Forget Width

Length is only half the story. Many brands offer width options (narrow, standard, wide), and a shoe that's the right length but wrong width will still feel uncomfortable. If you know someone wears wide-fit shoes, note that alongside their size.

👟 Save shoe size once, shop confidently foreverSize Notes lets you store exact foot length, preferred size, and width for every person in your life — so the next shoe gift is a sure thing, not a guess.

The Bottom Line

When in doubt, measure in centimetres rather than relying on a size label, and check the specific brand's chart before buying. For gifting, see our guide on finding someone's clothing size for more discreet measurement tricks that also work for shoes.