[LINK] Google AI Gives Wrong Size Conversion for Shoes

[Sylvano]

To be, real intelligence seems struggle with shore size conversions, especially given notorious variation between manufacturers.

I asked claud to give me the background on shoe sizing, and it responded:

<quote>

I'll provide you with the history and basis of the major shoe sizing systems used in these regions.

## United States Shoe Sizing System

The US system originated in the early 19th century and is based on the **Brannock system**, developed by Charles Brannock in 1925-1927. However, the foundation goes back earlier:

The system uses **barleycorns** as its basic unit - an old English measurement where one barleycorn equals 1/3 of an inch (8.46mm). The sizing works as follows:
- Size 0 corresponds to a foot length of 4 inches (for children)
- Each full size increases by 1/3 inch (one barleycorn)
- Adult men's sizing typically starts around size 6-7
- Women's sizes run approximately 1.5 sizes smaller than men's for the same foot length

The system became standardized across American shoe manufacturers in the mid-20th century, though there can still be variations between brands.

## European Union Shoe Sizing System

The European system, also called the **Paris Point system** or **Mondopoint**, has its roots in 18th century France:

- Based on the metric system using millimeters
- Each size represents a 6.67mm (2/3 centimeter) increment in foot length
- Size calculation: (foot length in mm + 12mm) ÷ 6.67
- The additional 12mm accounts for toe room and comfort
- This system was adopted widely across continental Europe and later became the EU standard

The European system is considered more precise than the US/UK systems because it's based on actual foot measurements rather than shoe last measurements, and it uses consistent metric increments.

## British-Based Colonial System (UK System)

The British system predates both American and European systems and has influenced sizing in former British colonies including Canada, Australia, New Zealand, South Africa, and India:

**Historical Development:**
- Originated in medieval England using barleycorn measurements
- King Edward II standardized the barleycorn as 1/3 inch in 1324
- The system was based on shoe last sizes rather than foot measurements

**How it works:**
- Uses the same barleycorn unit as the US system (1/3 inch increments)
- However, the starting point differs from the US system
- UK adult sizes typically run about one size larger than US sizes
- For example, a US men's size 9 equals approximately a UK size 8

**Colonial Influence:**
Many former British colonies maintained variations of this system, though some have transitioned to other systems over time. Countries like Australia and New Zealand still predominantly use UK sizing, while Canada uses a hybrid of US and UK systems depending on the manufacturer.

## Key Differences and Modern Usage

The fundamental difference lies in their measurement basis:
- **US/UK systems**: Based on shoe last (mold) sizes with barleycorn increments
- **European system**: Based on actual foot length measurements in metric units

Today, many international shoe brands include multiple size conversions on their products, though conversion between systems isn't always perfectly consistent due to different fitting philosophies and manufacturing tolerances in each tradition.

The persistence of these different systems reflects both historical trade patterns and the practical difficulties of standardizing something as variable as human foot dimensions across different populations and cultural preferences for shoe fit.​​​​​​​​​​​​​​​​

</quote>


Regards
Sylvano

> On 4 Jun 2025, at 9:18 am, Tom Worthington <tom.worthington at tomw.net.au> wrote:
> 
> I wanted to convert a shoe size from European to US. So I typed "eu38 shoe size us mens" into Google search. The AI result was: "A EU 38 shoe size for men in the US is typically a size 7 or 7.5. Some sources might list it as 7.5".
> 
> There was a small image of a chart from Bespoke Unit, next to the text. When enlarged this indicated a EU 38 was a US 6. https://draft.blogger.com/blog/post/edit/16502818/2980408283363443317#
> 
> However, the Wikipedia and other sources I checked, had a EU 38 shoe as between US 5 and 6.5 https://en.wikipedia.org/wiki/Shoe_size
> 
> 
> --
> Tom Worthington http://www.tomw.net.au
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