Shoe Size and Width Estimate
Estimate rough US, UK, EU and Japan shoe references from foot length and width.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
The size estimates use simplified formulas based on foot length; the width indicator uses foot width divided by length. These are model outputs, not a universal conversion chart. ISO 19407:2023 describes foot-length-based conversion tables as consumer guidance because sizing systems differ. Measure both feet and check the shoe maker’s chart.
Choose the calculation that matches your task
This estimator uses foot length, foot width and the selected sizing profile to show size and width indicators. The related converter uses foot length without a width input and lists multiple regional reference labels. Both use simplified models; check the actual shoe maker’s chart.
Worked example
calculated with the default values below
Measurement unit Centimetres · Foot length (selected unit) 26 · Foot width (selected unit) 9.5 · Shoe type Men's US size 8.7 · UK size 7.7 · EU size 41.0 · Japan size 26.0 · Width-to-length model indicator Standard
General background references
Disclaimer
These calculators give general estimates. Sizing, pricing, availability and standards vary by brand, retailer and country, so treat the output as a starting point and confirm it against the seller's or authority's own figures.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
US = 3L÷2.54 − a; UK = 3L÷2.54 − 23; EU = 1.5L + 2; JP = L
- L
- Foot length (cm)
- W
- Foot width (cm)
- a
- 22 men or 21 women
- US/UK/EU/JP
- Approximate size references
L is foot length in centimetres; a = 22 (men) or 21 (women). Width indicator uses foot width ÷ foot length with model thresholds 0.34, 0.38 and 0.42. These are approximate formulas; ISO 19407:2023 provides guideline conversion tables because systems differ.
Frequently asked questions
Are these shoe sizes exact conversions?
No. The calculator uses simplified foot-length formulas for US, UK, EU and Japan labels, plus a width-to-length ratio indicator. ISO 19407:2023 provides foot-length-based conversion tables as guidance because regional systems have developed differently. Use the specific shoe maker’s chart and measure both feet.