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Shoe Size Converter

Converts an adult shoe size between US men's, US women's, UK, EU (Paris point) and centimetre foot-length (Japanese / Mondopoint) sizing with the adult formulas of the Wikipedia 'Shoe size' article, snapping to the nearest half UK size of the adult chart (UK 3–14).

When to use

You have a shoe size in one system, or a measured foot length in centimetres, and need the equivalent adult US, UK, EU or centimetre size.

Do not use when: You need children's sizes (different scales), width fittings, or an exact match for a specific brand — brand charts differ by up to a full size, so use the brand's own table; to convert foot lengths between units use length.

Formula

foot_in = (UK + 23) / 3 = (US_men + 22) / 3 = (US_women + 20.5) / 3; cm = foot_in × 2.54 = (EU − 2) / 1.5; UK = 3 × foot_in − 23 rounded to the nearest 0.5 (chart UK 3–14); US_men = UK + 1; US_women = US_men + 1.5; EU = 1.5 × cm + 2 rounded to the nearest 0.5; JP = cm rounded to the nearest 0.5

Adult formulas from the Wikipedia 'Shoe size' article: the UK/US barleycorn scale (1/3 inch per size, US men's one size above UK) and the EU Paris point (2/3 cm per size, including the 2-point last allowance). The result is the chart row nearest to the input, so converting back and forth can move by half a size; manufacturers' charts deviate by up to one full size and their cm/Japanese labels typically run 0.5–1 cm larger than the measured foot.

Inputs

Parameter	Type	Unit	Required	Description
`size`	number		yes	The size number in the chosen system (for cm: the measured foot length in centimetres). Range: ≥ 0, ≤ 60
`system`	enum: us_men \| us_women \| uk \| eu \| cm		yes	System of the entered size.

Outputs

Output	Type	Unit	Description
`us_men`	number		US men's size = UK + 1.
`us_women`	number		US women's size = US men's + 1.5 (common retail scale; athletic/FIA charts use +1).
`uk`	number		UK size, the nearest half size of the adult chart (3–14).
`eu`	number		EU (Paris point) size = 1.5 × foot length in cm + 2, rounded to the nearest half size.
`cm`	number	cm	Foot length of the chart row, (UK + 23) / 3 inches in cm; the basis of Japanese and Mondopoint sizing.
`jp`	number	cm	Japanese (JIS) size = foot length in cm rounded to the nearest 0.5.
`foot_length_in`	number	in	Foot length of the chart row in inches.
`note`	string		Chart row used and the brand-variation caveat.

Example

US men's 10: {"size":10,"system":"us_men"} → {"us_men":10,"us_women":11.5,"uk":9,"eu":42.5,"cm":27.1,"jp":27,"foot_length_in":10.67}

24 cm foot length: {"size":24,"system":"cm"} → {"uk":5.5,"us_men":6.5,"us_women":8,"eu":38,"cm":24.1,"jp":24}

GET https://tttkmbb.com/api/v1/calculate/shoe-size?size=10&system=us_men

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/shoe-size (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/shoe-size · Markdown: https://tttkmbb.com/everyday/shoe-size.md · JSON definition: https://tttkmbb.com/everyday/shoe-size.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="shoe-size"
OpenAPI operationId: convert_shoe_size
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

Shoe size – sizing systems and adult conversion formulas (Wikipedia) (reference)

FAQ

Why does my brand's chart give a different EU or cm size?

Brands size on their own lasts: EU labels vary by about ±1 and cm/Japanese labels usually include 0.5–1 cm of toe room beyond the measured foot. This tool applies the published formula relations, so treat the result as a starting point.

Which US women's scale is used?

The common retail scale (women's = men's + 1.5). Athletic brands using the FIA scale label women's shoes only one size above men's; subtract 0.5 for those.

How do I measure foot length?

Stand on paper, mark the heel and the longest toe, measure the distance in cm and use the larger foot; enter it with system cm.

Related calculators

Ring Size Converter — Ring sizes between US, UK, EU, Japan and millimetres.
Length Converter — Convert foot length between centimetres and inches.