Why Shoe Sizes Vary by Brand
Your converted size—US 9, EU 42, UK 8—is a starting point, not a guarantee. The same number can fit differently from one brand to the next. This page explains why: lasts, fit models, grading, and regional targets. It also shows how to use our Shoe Size Converter, Measurement Tools, and Brand Sizing Guides for more consistent fit. For the big picture on global systems, see our International Sizing System and Complete Global Size Chart Guide.
The last: why one size doesn’t fit all brands
The last is the mold or form a shoe is built on. Its shape—narrow, wide, high instep, toe room—varies by brand and even by style within a brand. So a US 9 from our Shoe Size Converter or CM to US Shoe Size tool tells you the length-based size; it does not tell you whether that brand’s 9 runs snug or roomy. Athletic brands often use performance-oriented lasts (e.g. Nike, Adidas); heritage or wide-fit brands may use roomier lasts (e.g. New Balance). Use our Foot Width Calculator and Understanding Shoe Width when length is right but fit feels wrong.
Fit models and grading
Brands grade sizes from a fit model—a reference foot or body. Different brands choose different reference proportions, so the same “size 9” can map to slightly different actual lengths and widths. Grading (how much each half or full size steps up) also varies. That’s why your converted size is a baseline: get it from our Foot Measurement Calculator or Shoe Size Converter, then check the brand’s chart. Our Nike vs Adidas Sizing and individual Brand Sizing Guides describe fit tendencies. Articles on brands that run small and brands that run large summarize common reports.
Regional and market targets
Brands often design for a primary market. Shoes aimed at Asian or European markets may use slimmer lasts; US-focused lines may run slightly larger. When you buy across regions, use our US to EU Size, UK to US Size, and EU, US, UK, Japan sizing system pages to convert correctly, then compare to the brand’s size chart for that region. The Shoe Size Guides and Measurement Guides hubs tie together converters, tools, and how-to guides.
How to use conversion and brand charts together
Step 1: Get your length-based size—measure your foot (see How to Measure Your Feet and printable foot measuring sheet) and use the Shoe Size Converter or Foot Measurement Calculator. Step 2: Check the brand’s official size chart for the product. Step 3: If the brand runs small or large (see our Nike, Adidas, Zara, H&M guides), adjust up or down. Step 4: For width issues, use the Foot Width Calculator and Shoe Width Guide. The Measurement Assistant combines foot and body measurement in one place.
Authority hubs, converters & measurement tools
Hubs (cross-links): Shoe Size Guides · Clothing Size Guides · Brand Sizing Guides · Measurement Guides
Main converters: Shoe Size Converter · Clothing Size Converter · CM to US Shoe Size · US to EU Size · UK to US Size
Measurement tools: Foot Measurement Calculator · Foot Width Calculator · Measurement Assistant · Measurement Tools
Master & authority: International Sizing System · Complete Global Size Chart Guide · Programmatic Index
Frequently Asked Questions
Why does the same shoe size fit differently in different brands?
Brands use different lasts (molds), fit models, and grading. There is no single global standard that every brand follows, so a US 9 in one brand can fit like a 9.5 in another. Use our Shoe Size Converter for a baseline, then check the brand's size chart.
What is a last in shoe sizing?
The last is the mold or form a shoe is built on. Its shape (narrow, wide, high instep) varies by brand and style. Length-based conversion gives you a number; the last determines how that number actually fits on your foot.
Should I use my converted size for every brand?
Your converted size (e.g. from our Shoe Size Converter or CM to US tool) is a starting point. Always check the brand's official size chart and our brand sizing guides for fit tendencies. When between sizes, size up for comfort or order two sizes if returns are easy.