Shoe sizing is more confusing than it should be -- three main systems, width fittings, and brands that all fit slightly differently. This guide explains the UK, EU and US scales, how to measure your own feet properly, what width and volume mean, and the spec numbers (drop, stack, weight) you will see quoted. For brand-specific conversions, every brand guide has its own sizing chart.

Sizing Systems

UK, EU & US Sizes

The three main sizing scales and why the same foot has three different numbers.

How they work

UK, EU and US scales each measure length differently, so one pair of feet might be a UK 8, EU 42 and US 9. EU sizing uses the Paris point (about 6.6mm per size); UK and US use a barleycorn (about 8.5mm) but start from different points.

Getting it right

Always check the brand's own conversion chart rather than assuming -- the gaps between systems are not consistent. Each brand guide on site carries its sizing conversion.

Half Sizes & Size Gaps

Why half sizes exist and how much length a single size really adds.

How they work

A full size is roughly 8.5mm of length and a half size about 4mm. Half sizes give a closer fit between the full steps, which matters because even a few millimetres changes how a shoe holds the foot.

Getting it right

If you are between sizes, the right choice depends on the shoe's shape and your foot volume -- often size up for a roomy toe box, stay true for a snug performance fit.

Men's, Women's & Kids' Sizing

How the scales shift between men's, women's and children's shoes.

How it works

Men's and women's UK sizes share a scale but women's lasts are usually cut narrower with a lower volume. US sizing splits men's and women's by about 1.5 sizes. Kids' sizing restarts its own scale and changes fast as feet grow.

Getting it right

Unisex trainers are usually listed in men's UK sizes -- women often size down by around 1.5 from a US men's number. Check the listing's gender scale before ordering.

Width Fittings

The letter codes (D, E, EE) that describe how wide a shoe is cut.

How they work

Width fittings run from narrow to wide -- commonly D (standard men's), E, EE and beyond for wider feet, and B for standard women's. Not every brand offers them, but where they do, the same length comes in different widths. See the foot-shape section in the fit hub.

Getting it right

If shoes pinch across the ball of the foot but the length is right, you need a wider fitting, not a longer shoe. Brands like New Balance and some boots offer multiple widths.

Measuring Your Foot

Measuring Foot Length

The right way to measure your foot at home for an accurate size.

How to do it

Stand on a sheet of paper at the end of the day (feet swell), mark the heel and longest toe, and measure the distance. Do both feet -- they often differ -- and size to the larger one. Compare against the brand's size chart in centimetres.

Why it matters

Standing while measuring loads the foot to its real length. Measuring sitting down or in the morning gives a size that turns out too small once you are on your feet.

Measuring Foot Width

How to find your width fitting, not just your length.

How to do it

With your foot on the paper, mark the widest points across the ball of the foot and measure between them. Compare to the brand's width guide where one exists, or use it to judge whether to size up for room.

Why it matters

Two feet of the same length can need very different widths. Knowing your width stops you buying longer shoes just to get more room across the foot.

Instep & Volume

The height and girth of your foot -- why some shoes feel tight even in the right size.

How it works

The instep is the top of the foot; its height sets how much volume a shoe needs. A high-volume foot can feel crushed in a low-volume shoe even at the correct length and width.

Why it matters

If a shoe is the right size but feels tight over the top or hard to lace down, it is a volume mismatch. Lacing technique and shoe choice fix it -- see the fit hub.

Why Brands Fit Differently

The same size in two brands rarely fits the same -- here is why.

How it works

Every shoe is built on a last, the foot-shaped mould that sets length, width, toe shape and volume. Two brands using the same nominal size but different lasts will fit differently. It is the main reason for size confusion.

Why it matters

You cannot assume your size carries across brands. Always check each brand's sizing guide -- the construction hub explains the last in full.

Spec Numbers

Drop (Spec Number)

The heel-to-toe height figure quoted in millimetres on running shoes.

What it is

Drop is the millimetre difference between heel and forefoot stack height. Quoted as a single number (e.g. 8mm), it tells you how the shoe tilts the foot and which stride it suits.

How to read it

High drop (10-12mm) suits heel-strikers and eases the calf; low drop (0-6mm) loads the lower leg and suits a midfoot landing. The sole-technology hub explains the effect in full.

Stack Height & Weight

The two numbers that tell you how cushioned and how heavy a shoe is.

What they are

Stack height (mm) is the foam underfoot -- higher means more cushioning. Weight (grams) is quoted per single shoe in a stated size; lighter feels faster but often means less foam and durability.

How to read them

Compare like for like: weight is meaningless without the size it was measured at, and a high stack with a low weight signals a modern lightweight foam. Both are in the sole-technology hub.

Reading a Size Chart

How to use a brand's conversion chart instead of guessing your size.

What it is

A size chart maps foot length in centimetres to that brand's UK, EU and US sizes. Because brands differ, the chart -- not your usual number -- is the reliable way to size a new brand.

How to read it

Measure your foot in cm, find that length on the chart, and take the size next to it. Every brand guide on site links its own conversion chart, such as the On sizing conversion and Salomon conversion.