# 靴サイズ変換

> Convert shoe sizes between US men's and women's, UK, EU, India, Japan and Mondopoint via foot length, using the ISO/TS 19407 formulas.

操作できるページ：https://www.calcopenly.com/ja/conversion/shoe-size-converter
分野：単位換算ツール

Adult shoe sizes in the US men's, US women's, UK, Indian, EU, Japanese and Mondopoint systems all map to a foot length. The converter turns a size into a foot length L in millimetres with the ISO/TS 19407 formulas, then reads it on the target scale: EU = 3L/20 + 2 and UK = 3L/25.4 − 23, with US men's one size above UK and US women's two above.

Use it when buying shoes labelled in another country's system. The default, US men's 10, corresponds to a 270.9 mm foot, which is EU 42.6 before rounding and EU 43 after. Converted sizes round up to the next half size (5 mm steps for Japan and Mondopoint), as the specification recommends, so the answer errs towards room rather than a tight fit.

Brands cut their lasts differently, so compare the result with the brand's own foot-length chart. The formulas cover adult feet from 200 to 340 mm; children's sizes follow different formulas.

## 入力

- **Size**
- **変換元** (選択肢：US men's, US women's, UK, India (UK sizes), EU (Paris points), Japan (cm), Mondopoint (mm))
- **変換先** (選択肢：US men's, US women's, UK, India (UK sizes), EU (Paris points), Japan (cm), Mondopoint (mm))

## 結果

- Converted size — 主な結果
- Foot length (mm)
- US men's
- US women's
- UK
- India
- EU
- Japan (cm)
- Mondopoint (mm)

## 計算式

$$
\begin{gathered} L = \text{foot length (mm)} \\ \text{EU} = \tfrac{3L}{20} + 2 \\ \text{UK} = \tfrac{3L}{25.4} - 23 \\ \text{US men} = \text{UK} + 1 \\ \text{US women} = \text{UK} + 2 \end{gathered}
$$

## 計算例

### US men's 10 in EU

- Size: 10
- 変換元: US men's
- 変換先: EU (Paris points)
- **Converted size: 43**
- **UK: 9**
- **US women's: 11**
- **Mondopoint: 275 mm**
- **Japan: 27.5 cm**
- **Foot length: 270.9 mm**
- 照合元：Wikipedia ISO/TS 19407 adult table: US men 10 = UK 9 = US women 11 at 270.9 mm; the next sizes at or above that length are EUR 43 (273.3 mm) and Mondopoint 275

### EU 42 in UK and US

- Size: 42
- 変換元: EU (Paris points)
- 変換先: UK
- **Converted size: 8.5**
- **US men's: 9.5**
- **US women's: 10.5**
- 照合元：Wikipedia ISO/TS 19407 table: EUR 42 = 266.7 mm, where UK 8.5 / US men 9.5 sit; FIA women's scale = men's + 1

### Exact boundary: Mondopoint 250 is EU 39.5

- Size: 250
- 変換元: Mondopoint (mm)
- 変換先: EU (Paris points)
- **Converted size: 39.5**
- **UK: 7**
- **US men's: 8**
- 照合元：Wikipedia ISO/TS 19407 table: 250.0 mm row lists Mondopoint 250 and EUR 39.5; UK 6.5 is 249.8 mm, so the next UK size up is 7 (254.0 mm)

### Large size: UK 12 in EU

- Size: 12
- 変換元: UK
- 変換先: EU (Paris points)
- **Converted size: 46.5**
- **US men's: 13**
- 照合元：Wikipedia ISO/TS 19407 table: UK 12 = 296.3 mm; EUR 46.5 = 296.7 mm is the next size up

### Japan 26.5 cm in US men's

- Size: 26.5
- 変換元: Japan (cm)
- 変換先: US men's
- **Converted size: 9.5**
- **India: 8.5**
- 照合元：Wikipedia ISO/TS 19407 table: 265 mm falls between UK 8 (262.5 mm) and UK 8.5 (266.7 mm); rounded up, UK/India 8.5 = US men 9.5

## よくある質問

### What is a US men's 10 in EU size?

EU 43. Under ISO/TS 19407, US men's 10 fits a 270.9 mm foot, which works out to EU 42.6; converted sizes are rounded up to the next half size, giving 43. The same foot is UK 9, India 9, US women's 11, Japan 27.5 cm and Mondopoint 275.

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

Subtract 1 on the FIA (Footwear Industries of America) scale used here: US women's 9 is US men's 8. Many US brands use the common scale instead, where women's sizes are men's plus 1.5, so women's 9 is men's 7.5. UK sizing is nominally the same for men and women, although some manufacturers number women's UK sizes differently.

### Why don't EU and UK sizes line up one to one?

They count in different units. One EU size is a Paris point, 2/3 cm (6.67 mm) of shoe length; one UK or US size is a barleycorn, 1/3 inch (8.47 mm). A full UK size therefore spans 1.27 EU sizes, and no adult UK size falls exactly on a whole or half EU size, so every conversion between the two rounds.

### What is Mondopoint?

Mondopoint (ISO 9407) sizes a shoe by the foot length it fits, in millimetres, so a 270 mm foot is Mondopoint 270. It is the main system in Japan, which writes it in centimetres (27 cm), and in China, Russia and South Korea. Ski boots, skates, pointe shoes and NATO military footwear also use it.

### Are Indian shoe sizes the same as UK sizes?

Yes. Adult shoes in India, like those in the UK, Ireland, Pakistan and South Africa, are sized in barleycorns from the length of the last, so India 9 is UK 9 and US men's 10. Mondopoint is an optional second system in India, as it is in the UK.

### 「靴サイズ変換」の精度はどのくらいですか？

精度は入力値と計算方法の前提に依存します。十進演算には有効数字50桁を使いますが、推定、数値計算手法、元データの精度はそれより低い場合があります。表示の丸め処理でこれらの制約がなくなるわけではありません。 独立した出典の解答と照合した計算例：5。 例えば、「US men's 10 in EU」はWikipedia ISO/TS 19407 adult table: US men 10 = UK 9 = US women 11 at 270.9 mm; the next sizes at or above that length are EUR 43 (273.3 mm) and Mondopoint 275と照合しています。

### この計算方法の出典は何ですか？

ISO/TS 19407:2015 — Footwear — Sizing — Conversion of sizing systems; Wikipedia — Shoe size: ISO 19407 formulas and adult size equivalence table.

## 出典

- [ISO/TS 19407:2015 — Footwear — Sizing — Conversion of sizing systems](https://www.iso.org/standard/62349.html)
- [Wikipedia — Shoe size: ISO 19407 formulas and adult size equivalence table](https://en.wikipedia.org/wiki/Shoe_size#ISO_19407_and_shoe_size_conversion)