True-to-Size Millimeter Sizing Comparison
Sperry AO 2 Eye Leather MM vs Sperry Billfish 3 Eye
Detailed size conversion chart, cavity measurements in millimeters, and crowd-sourced fit advice for choosing your perfect size.
Interactive Size Converter
Select what size you wear in the AO 2 Eye Leather MM to see your calculated size in the Billfish 3 Eye.
Complete Size Conversion Matrix
Direct millimeter-calibrated mapping comparing all available sizes between both shoes.
| AO 2 Eye Leather MM (US) | Internal Cavity | Billfish 3 Eye Equivalent | Match Accuracy | Fit Difference |
|---|---|---|---|---|
| US 3.5 | 240 mm | US 7 | 0% | +27.2 mm |
| US 4 | 243 mm | US 7 | 0% | +24.2 mm |
| US 4.5 | 247 mm | US 7 | 0% | +20.2 mm |
| US 5 | 250 mm | US 7 | 0% | +17.2 mm |
| US 5.5 | 253 mm | US 7 | 0% | +14.2 mm |
| US 6 | 257 mm | US 7 | 0% | +10.2 mm |
| US 6.5 | 260 mm | US 7 | 15% | +7.2 mm |
| US 7 | 267 mm | US 7 | 98% | +0.2 mm |
| US 7.5 | 270 mm | US 7.5 | 98% | +0.2 mm |
| US 8 | 273 mm | US 8 | 98% | +0.2 mm |
| US 8.5 | 277 mm | US 8.5 | 98% | +0.2 mm |
| US 9 | 280 mm | US 9 | 98% | +0.2 mm |
| US 9.5 | 283 mm | US 9.5 | 98% | +0.2 mm |
| US 10 | 287 mm | US 10 | 98% | +0.2 mm |
| US 10.5 | 290 mm | US 10.5 | 98% | +0.2 mm |
| US 11 | 293 mm | US 11 | 98% | +0.2 mm |
| US 11.5 | 297 mm | US 11.5 | 98% | +0.2 mm |
| US 12 | 300 mm | US 12 | 98% | +0.2 mm |
| US 12.5 | 303 mm | US 12.5 | 98% | +0.2 mm |
| US 13 | 307 mm | US 13 | 98% | +0.2 mm |
| US 14 | 313 mm | US 14 | 98% | +0.2 mm |
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Frequently Asked Questions
How does the AO 2 Eye Leather MM size compare to the Billfish 3 Eye?
Both shoes share a very similar length profile. We recommend ordering your standard size in both. The AO 2 Eye Leather MM has an internal fit offset of 0mm compared to 0.16mm for the Billfish 3 Eye.
Do these shoes fit wide feet comfortably?
The AO 2 Eye Leather MM has a standard medium width profile, while the Billfish 3 Eye is snug/narrow.