UK shoe sizes to EU and US: a conversion guide, and why insoles matter

As a rough guide, a UK women's shoe size is usually two lower than the US women's size and about 33 lower than the EU size: a UK 5 is typically a US 7 and an EU 38. A UK men's size is usually one lower than the US men's size, so a UK 9 is roughly a US 10 and an EU 43. But shoe sizing is far from exact, so the most reliable check when buying second-hand is the insole length in cm.

Second-hand shoes come with labels in every system, often printed inside the tongue or on the sole. Here is how to read them and how to make sure a pair will fit.

Women's shoe sizes

These are the conversions most commonly used. Brands may differ by half a size or more.

• UK 3 is usually EU 36 and US 5.
• UK 4 is usually EU 37 and US 6.
• UK 5 is usually EU 38 and US 7.
• UK 6 is usually EU 39 and US 8.
• UK 7 is usually EU 40 or 41 and US 9.
• UK 8 is usually EU 41 or 42 and US 10.

Half sizes follow the same pattern, though EU sizes do not always have halves, so a UK 5.5 might be labelled EU 38.5 or rounded to EU 38 or 39.

Men's shoe sizes

• UK 7 is usually EU 41 and US 8.
• UK 8 is usually EU 42 and US 9.
• UK 9 is usually EU 43 and US 10.
• UK 10 is usually EU 44 or 45 and US 11.
• UK 11 is usually EU 45 or 46 and US 12.
• UK 12 is usually EU 47 and US 13.

Some trainers and unisex shoes are labelled in men's sizes only. If you usually wear women's sizes, a unisex UK size is often the same, but the US figure on the label will be the men's one, not the women's.

Children's shoe sizes

Children's shoes in the UK use their own scale, starting with infant sizes and running up to around a 13, before restarting at 1 for older children. Because feet grow quickly, the insole length matters even more here than for adults. Leave a little growing room, and never buy children's shoes so small that toes touch the end.

Why shoe sizes vary

The UK, EU and US systems were built on different units and starting points, and each brand also has its own lasts, the foot-shaped moulds shoes are built around. That means:

• the same size can fit differently from one brand to another
• the same brand can fit differently between styles, such as a boot and a trainer
• width varies as well as length, and most labels say nothing about width
• older shoes may have been sized differently from current ones

Measure the insole instead

The insole length is the distance inside the shoe from the back of the heel to the tip of the toe. It is the single most useful figure for buying shoes second-hand.

How to measure your own feet

1. Stand on a sheet of paper against a wall, with your heel touching the wall.
2. Mark the tip of your longest toe.
3. Measure from the wall to the mark in cm.
4. Do both feet, and use the longer one.

How to measure a shoe you already own

Take a pair that fits you well. Remove the insole if it comes out and measure it from heel to toe. If it does not come out, slide a tape measure or a strip of card inside and mark where it reaches the toe.

Your comfortable insole length will usually be a little longer than your foot, to leave room to move. Comparing with a pair that already fits is the easiest way to know how much room you like.

Checking a second-hand pair before you buy

• Ask for the insole length in cm, measured the same way as yours.
• Ask about width if you have wide or narrow feet. A seller can tell you whether the shoes felt roomy or narrow on them.
• Look at the insoles in the photos. Deep impressions mean they have shaped to someone else's foot.
• Check the soles and heels for wear. Our guide to buying second-hand winter boots has a full list of checks that also apply to everyday shoes.

On Rewear, tap Message the seller to ask for any figure that is missing from a listing. Our guide to measuring clothes for buying online explains the insole measurement along with the others.

Selling shoes

Give the size exactly as printed inside the shoe, including which system it is in, and add the insole length in cm. Photograph the soles, heels, toes, insoles and the size label in daylight. Clean them first, and mention any wear or marks plainly. A pair of shoes usually fits a large parcel, which on Rewear is described as about a shoebox, and boots often need extra large. Our guide to posting clothes cheaply in the UK explains how parcel size works.

The short version

UK women's sizes are usually two lower than US women's and around 33 lower than EU; UK men's are usually one lower than US men's. Brands and styles vary, so ask for the insole length in cm and compare it with a pair that fits you.