Shoe size calculator

How do I measure my foot for a shoe size?

Stand on a sheet of paper against a wall with your heel touching the wall, mark the tip of your longest toe, and measure from the wall to the mark. Do both feet and use the longer one. Enter that length in inches or centimeters. The calculator adds a toe allowance (2/3 inch by default), because a shoe is built on a last that is longer than the foot.

How are US, UK and EU shoe sizes related?

All three count in fixed steps along the length of the shoe last. The UK and US sizes step by one third of an inch (a barleycorn); EU sizes step by one Paris point, two thirds of a centimeter. The scales start from different zero points, which is why the same foot is a UK 9, a US men's 10 and about an EU 43.

What is the formula for shoe size?

With the last length L in inches: UK adult = 3 × L − 25; US men's = 3 × L − 24; US children's = 3 × L − 11.75; EU = L in centimeters × 3 ÷ 2. US women's is the men's number plus 1½ in the usual retail convention. The last is the foot plus a toe allowance, about 2/3 inch for a Brannock device.

What is Mondopoint?

Mondopoint is the shoe-size system of the international standard ISO 9407. It labels a shoe with the foot length it is made for, in millimeters, and optionally the foot width: a label of 270/100 means a foot 270 mm long and 100 mm wide. Sizes step by 5 mm for ordinary shoes (7.5 mm for protective footwear). Because it is a plain length, it does not depend on a national scale.

Why does my size differ between brands?

Because the standards define how sizes are numbered, not the shape of the last. Each maker chooses the toe room, the width and the shape of its own lasts, and many round sizes in half steps. A difference of half a size to a whole size between brands is normal, and the calculator says so in the result: treat its answer as the starting point and check the maker's own chart.

How do I convert men's shoe sizes to women's?

Add 1½ to a men's US size to get the women's size: a men's 10 is a women's 11½. Some brands use a difference of one size for unisex shoes, so check the label. In the opposite direction, a women's 10 corresponds to a foot of 10.17 inches, the same as a men's 8.5.

What about children's sizes?

Children's shoes use their own scale in the US and UK (the formulas have different offsets), which runs up to US 13 or UK 13½; after that sizes restart at 1 on the youth or adult scale. Kids' feet grow quickly, so fit matters more than the number on the box. Measure often and leave room, using the maker's chart for the exact size.

How the calculator works

Every numeric scale counts steps of a fixed length along the shoe's last, starting at a zero point. The last is a form 2 barleycorns (2/3 inch) longer than the foot in a Brannock device, which sets the default allowance. The calculator adds the allowance to the foot to get the last length, then applies the formulas: UK adult = 3 × L − 25, US men's = 3 × L − 24, EU = L in centimeters × 1.5. Results are rounded to the nearest half size, and Mondopoint is the foot length in millimeters rounded up to the next 5 mm. Entering a size instead of a length runs the formulas backwards, which is how you can tell how long a foot a given size is built for: UK 1 is a foot of 8.00 inches, US men's 1 is 7.67 inches and EU 42 is 10.36 inches.

Worked example

A man's foot measures 27 cm, or 10.63 inches. Adding 2/3 inch gives a last of 11.30 inches. UK = 3 × 11.30 − 25 = 8.89, which rounds to 9. US men's = 3 × 11.30 − 24 = 9.89, rounds to 10; the women's equivalent is 11.5. EU = 28.69 cm × 1.5 = 43.04, so 43. Mondopoint is 270. A maker that allows only 1/2 inch of toe room would put the same foot at US men's 9.5, so the answer depends on the brand. A woman with a foot of 9¼ inches (23.5 cm) comes out at US women's 7.5, UK 5 and EU 38. For a child with a foot of 6½ inches the children's scale gives US 10 and UK 9.5; at 8.1 inches the child is past the end of the children's scale and moves to youth size US 2.5.

Limits of any shoe size calculator

A size is a label, not a measurement of fit. Width is not included: the same length is sold in several widths, and a narrow shoe in your length can feel too small while a wide one in the next size down feels loose. Feet change through the day and over the years, and the two feet usually differ. The conversion rules come from the common formulas for the last length; a maker may use its own steps, rounding or allowance, and national standards are not identical (the UK scale, for example, is not formally standardized). A pair that is hard to size, such as boots or running shoes, is best fitted by trying it on, or by using the maker's chart with a Mondopoint length.

Common mistakes

Measuring the shoe, not the foot, which gives a number about 2/3 inch too large. Using one scale for all: a men's 7 and a women's 7 are different lengths (a women's 8½ matches a men's 7). Ignoring the end of the children's scale, so that a youth size 1 is bought as if it were a child's 14. And buying online by a converted number alone: if the maker publishes a foot-length chart in centimeters, that chart beats any general conversion.

Sources and related calculators

Sources: ISO 9407 (Mondopoint system of sizing and marking, 2019 edition) for the foot-length system and 5 mm steps; the last-length formulas for UK, US and Paris-point sizes and the Brannock allowance as summarized in the Wikipedia article “Shoe size” (read October 27, 2026). Size charts of individual brands are not used here, because each brand sizes its own lasts. Related: ring size calculator, paper size calculator, tire size calculator and age calculator.