Shoe Size Converter API

About the Shoe Size Converter API

A shoe size converter API that takes one size, the system it is in and a gender category, and returns the equivalent in every other system. Send US men's 9 and get back the UK, Australian, Mexican and Korean sizes together, each rounded to one decimal so you can match it to the nearest half size you stock.

Retailers and marketplaces use it to build a shoe size conversion chart, for example EU to US shoe sizes, to show a local size next to an imported product's label, and to normalise sizes from suppliers in different regions into one catalog field. Men's, women's, unisex and children's sizing each use their own offsets.

The Free plan returns US, UK, Australian, Mexican and Korean equivalents with the input size, region and gender echoed back. Paid plans add the EU size, the Japanese size and the foot length in centimetres. Sizing varies between brands, and every response includes a note saying the conversion is approximate.

How it works

Shoe Size Converter turns the input into a length in centimetres, then derives every other system from that length with linear formulas. US, UK and Australian sizes step 0.847 cm per size from a gender-specific offset. For US sizing, men's sizes start from 21.5 cm, women's from 20.2 cm, unisex from 21 cm and children's from 9.5 cm; UK and Australian sizes use slightly higher offsets of 22.3, 21, 21.7 and 10.3 cm. An Australian input with gender=child falls back to the unisex offset.

The other systems ignore gender. EU size is centimetres divided by 0.667. Japanese size equals the centimetre value. Mexican size uses the 0.847 step from a 17.5 cm offset. Korean size is the length in millimetres, so kr is ten times cm.

from accepts us, uk, eu, cm, jp, au, mx or kr; gender accepts men, women, unisex or child and defaults to unisex. size is parsed as a decimal number. Every value in conversions is rounded to one decimal place and is not snapped to a half size, so a US men's 9 becomes UK 8.1 rather than 8 or 8.5. input_region is the source system in upper case, and input_size and gender echo what was used.

Because the formulas are linear, very small or very large inputs extrapolate rather than fail, which can produce sizes no manufacturer makes. On the Free plan eu, cm and jp are removed from conversions.

What people use it for

E-commerce

Help international customers find their correct shoe size when shopping from different countries

Travel Planning

Convert shoe sizes when shopping abroad or purchasing from international retailers

Size Charts

Generate comprehensive size charts for footwear products with multiple regional standards

Retail Apps

Integrate size conversion features into shopping apps to improve customer experience

Ways to call it

One endpoint, many ways in — REST with JSON, XML, YAML and CSV, plus GraphQL and an MCP interface for AI agents.

JSON

Default REST response

XML

Markup format

YAML

Human-readable

CSV

Tabular export

Beta

GraphQL

Query language

New

MCP

For AI agents

Request parameters — GET /v1/shoesizeconverter

Sent in the query string. Premium parameters are accepted on every plan but only take effect on plans that include them. Anything not listed here is dropped rather than passed through.

Required

Optional

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curl "https://api.apiverve.com/v1/shoesizeconverter?size=9&from=us&gender=men" \
  -H "x-api-key: YOUR_API_KEY"

Authentication

Send your key in the x-api-key header. That is the only auth step — no token exchange, and no per-endpoint scope to configure.

Response — GET /v1/shoesizeconverter

Every APIVerve endpoint returns the same three top-level keys, so one response handler covers your whole integration: status, error and data. Only data changes shape.

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{
  "status": "ok",
  "error": null,
  "data": {
    "input_size": 9,
    "input_region": "US",
    "gender": "men",
    "conversions": {
      "cm": 29.1,
      "jp": 29.1,
      "us": 9,
      "uk": 8.1,
      "au": 8.1,
      "eu": 43.7,
      "mx": 13.7,
      "kr": 43.7
    },
    "note": "Sizes are approximate and may vary by manufacturer"
  }
}

Response fields

Paths are relative to data. Premium fields are absent rather than zeroed on plans that do not include them, so check for presence instead of comparing to 0.

Response headers

Every response carries your balance, so your own code always knows where it stands without polling anything. All four are exposed to browsers through CORS.

Errors

Read the HTTP status first, then error for the specific reason. The body names the parameter that has to change.

What a call costs — 1 credits per call

Credits are shared across every APIVerve API — one balance, one key, one bill. Failed requests never count against it, so a rejected input costs nothing.

Calls are what the credits buy at this API's rate — spend them here, on any of the other APIs, or across both. Nothing is reserved per endpoint.

Zero-code embed — one snippet, no backend

Drop an interactive Shoe Size Converter form onto any page. The widget calls the API for you, so no key ever appears in your markup and there is nothing to deploy.

Changelog — Shoe Size Converter API

Every change to this endpoint, newest first. Breaking changes ship as a new version and the previous one keeps serving — response fields are added, never removed or retyped in place, so an integration written against v1 keeps working.

Currently v1