Shoe Size Conversion

International Footwear Sizing Systems & ISO Standards

Global footwear manufacturers use diverse measurement units rooted in historical craftsmanship:

Primary Sizing Systems & Mathematical Formulations

• US & UK Barleycorn System: Based on the barleycorn.

• US Men's Size = 3 × L_last (in) - 22

• US Women's Size = 3 × L_last (in) - 20.5 = US Men's + 1.5

• UK Size = 3 × L_last (in) - 23 = US Men's - 0.5

• European Continental System (Paris Points): Based on the Paris point.

• EU Size = (3) / (2) × L_last (cm) = 1.5 × (L_foot (cm) + 1.5)

• Mondopoint / Japanese System (ISO 9407): Expressed directly in millimeters or centimeters of actual foot length (L_foot).

How to Measure Foot Length Accurately

• Stand barefoot on a piece of paper taped to a hard floor, with your heel against a flat wall.

• Mark the longest point of your foot (usually the big toe or second toe).

• Measure the distance from the wall edge to the mark in inches or centimeters.

• Measure both feet in the afternoon (when feet are slightly swollen) and fit to the larger foot.

How to Use This Calculator

Enter your Gender & Sizing Category — choose from Men's Sizing, Women's Sizing, Children / Youth Sizing, Input Standard / Reference System — choose from US Size, European Size (EU), UK / British Size, and Shoe Size or Foot Length Value (e.g. 9). Results update instantly as you type — adjust any value to compare scenarios.

The Formula

Formula Reference: Shoe Size Conversion

Input variables:

genderCategorySelect — Gender & Sizing Category

inputStandardSelect — Input Standard / Reference System

inputValueNumber — Shoe Size or Foot Length Value

Computed outputs:

usShoeSize — US Shoe Size

euShoeSize — European Size (EU)

ukShoeSize — UK / British Size

japanCmShoeSize — Japan / Mondopoint Size

footLengthInches — Foot Length

Mathematical relationships extracted from calculation logic:

usMen = val - 1.5

usWomen = usMen + 1.5

usKids = usMen + 12

euSize = Math.round((usMen * 1.333) + 30.5)

footIn = (usMen + 22) / 3

footCm = footIn * 2.54

Reference constants:

usMen = 9

Standard: NIST Handbook 44 and BIPM SI unit definitions

Worked Example

Shopping for European footwear with a US Men's size 9: Converting directly points to EU 42.5 (UK 8.5), matching a 26.2 cm foot length.

Understanding Your Result

Unit conversions are exact by definition within a given measurement system (e.g., 1 km = exactly 1,000 m). Cross-system conversions (metric to imperial) use defined exchange factors: 1 inch = exactly 2.54 cm; 1 pound = 0.45359237 kg. Round your converted result to match the precision of your original measurement — expressing more decimal places than your input justifies implies false accuracy. For regulatory, legal, or safety-critical applications, verify which measurement system is required by the applicable standard.