ForHosting KIT · Home, food & hobbies

UK to US shoe size converter

A UK 8 is a US 9 and a UK 5.5 is a US 6.5: the US scale sits one full size above the UK scale for the same gender. Enter the number on the box and choose men's or women's. Free in your browser.

Free
Runs in your browser
No sign-up
Your data stays on your device

Run — free How it works & API

Use it from WebAPIEmailTelegramApp soon

Worked example

If you enter

Size: 8
Gender: Men

You get

From: uk
To: us
Uk: 8
Us: 9

This UK to US shoe size converter turns a British size into the matching United States size using the standard one-size offset, for men or for women. Retailers and travelers treat the UK scale as one full size smaller than the same-gender US scale, so a UK 8 is a US 9 and a UK 5.5 is a US 6.5. Enter the number printed on a UK box and whether the pair is men's or women's; the engine adds one and returns the US size you would ask for in an American shop.

What the one-size difference means

Converting a UK shoe size to a US size answers a shopping question: if you wear a given British size, what number should you ask for in an American shop or on a United States product page. The two systems share the same half-size step, but they do not share a zero. The standard one-size offset used by retailers is that a UK size is one full size smaller than the same-gender US size.

Adding one therefore maps UK 7 to US 8, UK 8.5 to US 9.5, and UK 10 to US 11, for men or for women. This converter does not mix genders, does not jump to EU Paris points, and does not apply brand-fit slop: it adds the offset or it rejects the input. There is no Mondopoint millimetre table, no children's special scale, and no last-length inch column on this landing.

If you need a four-scale table that also lists EU and centimetres, use a broader shoe-size helper; this page is the dedicated UK-to-US conversion.

Where UK-to-US shoe conversion fits in shopping, travel, and software

People meet UK-to-US shoe conversion when a British web shop lists size 8 and a US return portal asks for the American size, when a traveler tries on a pair tagged only in UK numbers, or when a teacher asks students to apply a one-size offset without a laminated chart. Shoppers can pre-check a men's UK 9 against its US neighbour before they treat an international checkout as a sunk cost, and customer-care teams can answer “what is my UK size in US?” without arguing about brand last shape.

Contest and homework practice often needs a fast, offline source of conversions so solutions can be checked without a paper size chart under time pressure. Product and education tools use the split when a learner types a size and the interface must show a clean wearable US tag beside the original UK number.

What you can do with it

Order shoes from a US store with a UK size

Add one to a known UK adult size, for men or women, and use the US tag before you check out.

Travel and boutique fittings

Turn the number on a British box into the matching US size without a paper chart or a brand-specific fit table.

FAQ

What does the UK to US shoe size converter cost?

It is free in your browser on this page.

How is the US size defined?

The standard one-size offset is US = UK + 1 for the same gender.

What happens if the size is not a positive number?

Zero, negatives, NaN, Infinity, and non-numeric tokens are not converted.

Why do you ask for gender if the offset is always one?

The offset is the same, but the conversion is same-gender. A women's UK 6 is not a men's US 7; the response labels the US size as men's or women's so the tag is not mixed.

Does this include EU sizes or brand-fit differences?

No. This landing converts only UK to US with the one-size offset. EU, Mondopoint, children's special scales, and brand last-shape slop are out of scope.

Related tools

For developers — API access

Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.

API endpoint

POSThttps://api.kit.forhosting.com/life/uk-us-shoe-size

Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.

Call it from your stack

curl -X POST https://api.kit.forhosting.com/life/uk-us-shoe-size \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"size":8,"gender":"men"}'

const res = await fetch("https://api.kit.forhosting.com/life/uk-us-shoe-size", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "size": 8,
    "gender": "men"
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/life/uk-us-shoe-size",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "size": 8,
    "gender": "men"
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/life/uk-us-shoe-size", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"size":8,"gender":"men"}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"size":8,"gender":"men"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/life/uk-us-shoe-size", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "size": 8,
  "gender": "men"
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "life.uk_us_shoe_size",
  "status": "queued",
  "_links": {
    "result": "/tasks/tsk_…/result"
  }
}

The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.

Pricing

Per request$0.002

Published price — no tokens, no invented credits. A failed task is never charged.

Errors

HTTP	Code	Meaning
`401`	`unauthorized`	Missing or invalid API key.
`402`	`insufficient_balance`	Your balance doesn't cover the task price.
`404`	`unknown_type`	That task type doesn't exist.
`429`	`rate_limited`	Too many requests. Use the webhook instead of polling.

Technical notes

A size that is not a positive number is rejected as invalid_input instead of being silently clamped. Run it free in the browser before you check out, or call the API at $0.002 per successful request when a catalog, return desk, or packing list needs the same conversion.

What the one-size offset means and what the response contains

The response echoes the normalized UK size and gender, returns us and converted_size as the United States tag, reports the constant offset of one, and includes a short formula string and a readable message. A missing size, a missing gender, a non-finite size, or a size that is not a positive number fails with invalid_input.

How size and gender are read so results stay reproducible

The arithmetic is the same one-size offset in both cases. Optional leading plus signs and scientific notation on the numeric size are allowed when they parse as finite decimals; embedded spaces, hex prefixes, and non-numeric tokens are rejected with a message that names the field so a bad cell does not become a wrong pair of sneakers. Half sizes such as 7.5 and 9.5 are welcome and stay half sizes after the offset. Computation uses ordinary floating-point addition, then rounds the echoed fields to twelve decimal places so goldens stay stable across runtimes. The preferred field for the number on the box is size, but aliases value, uk, uk_size, and n are accepted so a form, a query string, or a spreadsheet column can reuse the same contract without renaming cells. Gender prefers gender, with aliases sex and wearer; allowed values are men and women because the conversion is same-gender: a men's UK size becomes a men's US size, and a women's UK size becomes a women's US size. The size must be a positive number: zero, negatives, NaN, and Infinity are invalid_input and are not billed. Pair the free browser run on this page with the priced API when you need that identical mathematical result inside a catalog import or return-desk script without re-implementing the one-size rule yourself.

Where UK-to-US shoe conversion fits in shopping, travel, and software

Developers call the same contract from scripts to seed deterministic test vectors for footwear calculators, to normalize user-entered sizes before a catalog demo, or to satisfy a product statement that demands a converted_size field rather than a hand-waved guess. On this page the work runs entirely in your browser; through the API each successful lookup costs $0.002, failed validation is not charged, and nothing is stored after the response returns. That split — free interactive exploration and a priced, identical API — matches the rest of the tier-A catalog and lets you move from a classroom demo to an automated pipeline without changing the mathematical result.

Integration use cases

Catalogs, returns, and test fixtures

Normalize size and gender into stable us and converted_size fields for product interfaces and continuous-integration assertions.

Read the full KIT documentation →

Run — free

Worked example

What the one-size difference means

Where UK-to-US shoe conversion fits in shopping, travel, and software

What you can do with it

Order shoes from a US store with a UK size

Travel and boutique fittings

FAQ

Related tools

For developers — API access

API endpoint

Call it from your stack

Example request

Example response

Pricing

Errors

Technical notes

What the one-size offset means and what the response contains

How size and gender are read so results stay reproducible

Where UK-to-US shoe conversion fits in shopping, travel, and software

Integration use cases

Catalogs, returns, and test fixtures

thank you