Shoe Width Standards (Brannock Width Scale)
Direct Answer
Shoe width classifications standardize the forefoot ball joint circumference and foot width relative to shoe length. Measured using the industry-standard Brannock Device, widths span from ultra-narrow (4A/AAAA) to maximum wide (6E/EEEEEE), with each letter step representing a 3/16-inch (4.76 mm) increase in ball circumference.
Source: The Brannock Device Company / SATRA Technical Standards
Specs
| Governing Standards | The Brannock Device / SATRA TM / ASTM F2413 |
| Standard Medium Width (Men) | D (Medium / Standard fit for North American men) |
| Standard Medium Width (Women) | B (Medium / Standard fit for North American women) |
| Circumference Step Increment | 3/16 inch (0.1875" / 4.76 mm) per letter width step for a given length |
| Narrow Width Scale | 4A (AAAA) | 3A (AAA) | 2A (AA) | A | B | C |
| Wide Width Scale | E | 2E (EE / Wide) | 3E (EEE) | 4E (EEEE / Extra Wide) | 6E (Maximum) |
| Relative Width Principle | Width is proportional to length (a Size 12B has the same width as a Size 9D) |
The 3/16-Inch Ball Circumference Scaling Rule
Shoe width is not measured across the sole in isolation; it represents the ball girth (circumference) measured around the widest metatarsal-phalangeal joint of the foot. For any specific shoe length size (e.g., US Men's 10):
- Moving from $D$ (Medium) to $EE / 2E$ (Wide) adds $3/8\text{ inch}$ ($9.5\text{ mm}$) in ball circumference.
- Moving from $D$ to $4E$ (Extra Wide) adds $3/4\text{ inch}$ ($19.0\text{ mm}$) in ball circumference.
Proportional Width Scaling Across Lengths
Because human feet naturally widen as they grow longer, letter widths are relative, not absolute. A shoe's physical width expands by approximately $1/12\text{ inch}$ ($2.12\text{ mm}$) with each full length size step:
- A Size $12\text{ B}$ (Narrow) has approximately the same physical width as a Size $10\text{ D}$ (Medium) and a Size $8\text{ EE}$ (Wide).
- For women, $B$ is standard medium, $A/2A$ is narrow, and $D$ is wide.