How These Size Charts Are Built

This site makes specific numerical claims about 35 brands, so here is exactly where the numbers come from, what is verified, and what is not.

Everything is keyed to foot length

Sizes are never converted from one size number to another. Each brand's chart is stored against measured foot length in centimeters, and a lookup matches your measurement to that brand's own row. That is why a single measurement can be read against every brand at once, and why a conversion between two brands goes through foot length rather than through a US-to-EU offset.

Sourcing rules

The brand's own published chart is preferred over any retailer's.
Where no brand chart is available, at least two independent sources must agree.
Where sources disagree by more than the precision being claimed, the brand is rejected rather than averaged.
A figure this site worked out rather than copied from a chart never outranks a published one. The October 2026 re-check found women's tables that had been generated from the men's, with the UK size moved along with the US; they were replaced by the brands' own women's charts.
Sources are listed on every brand page (152 across the site), so any figure can be checked against its origin.

That rule has teeth. Of the 35 brands here, 5 still show a standard youth scale for children rather than the brand's own: two because published sources disagree by more than a size with nothing to settle it, one because the only chart found was a shared industry scale published under a brand name, and two because no children's chart could be reached at all. Each of those brands says which case it is on its own page.

The trap that catches most size charts

Many brands publish more than one centimeter column, and only one of them is a foot length. The other is a shoe or last measurement, typically running 0.4cm to 1.5cm longer. KEEN, Teva, Mizuno, Dr. Martens and adidas all do this. A chart that quietly uses the wrong column will oversize nearly everyone who reads it.

Children's charts carry a second version of the same trap: some retailers publish figures with growing room already added, then also instruct parents to add growing room. Following both oversizes a child by close to a full size.

Children's sizing

30 of 35 brands publish children's data we could verify. The remaining 5 either publish none, or publish figures that disagree between sources. For those, the calculator uses a standard youth scale and says so on the result rather than presenting it as the brand's own. See the kids' size chart for the full comparison.

Width

14 brands publish genuine width fittings, and those are stored as the brand's own letters rather than normalized, because the letters do not mean the same thing across brands: a D is the standard men's fitting in most American sizing but Danner's wide women's fitting. For every other brand the calculator gives a general estimate and labels it as one. See the width chart.

Rounding and between-sizes

Where a measurement falls between two chart rows, you choose: round up, or take the nearest. Rounding up is the default for everyone, and matters most for children, since their feet keep growing between purchases. A measurement within a tenth of a millimeter of a chart row is read as being on that row: no tape measure resolves anything finer, and without that allowance a length typed in inches could land a fraction of a tenth of a millimeter past a row and be moved a whole size. Where a brand's own chart lists two sizes at the same centimeter, which happens in Nike's, Timberland's and Altra's published charts, the smaller is shown, which is the safer result under a round-up default.

Does a brand run small?

Each brand page answers this from the charts alone. Every foot length from 25 to 29 cm (men's) and 22.5 to 26 cm (women's), in 1 mm steps, is looked up in that brand's chart and in the other 34, the way the calculator reads a chart: rounding up between sizes. The brand's size is compared with the size the other brands give most often, and the average gap is the answer. A gap under 0.15 of a size is "in line with most brands"; up to 0.35 is "slightly"; larger gaps are given to the nearest half size, or as a range where they fall between two. The most common size is used rather than an average because women's charts follow two or three conventions: a 24 cm foot is a US 7 in some brands, a 7.5 in others and an 8 in a few, and an average would describe none of them. This compares published charts, which state how a brand means its sizes to fit; it says nothing about how a particular model feels.

What this cannot tell you

A size chart is a starting point, not a guarantee. Fit varies by model, last, material and how a shoe is laced. Brand charts describe the brand's intent, not any particular shoe. Where a brand's own guidance contradicts its chart (Altra advising extra room, UGG advising to size down because sheepskin compresses), that guidance is shown in the brand's fit notes rather than folded silently into the numbers.

Corrections

Manufacturers revise their charts. Every brand page carries the date its data was last reviewed. If you find a figure that disagrees with a brand's current published chart, please report it. Corrections are applied to the source data so every page that uses it updates together.