True-to-Size Millimeter Sizing Comparison
Reef Fanning W vs Reef Reef Neptune
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 Fanning W to see your calculated size in the Reef Neptune.
Complete Size Conversion Matrix
Direct millimeter-calibrated mapping comparing all available sizes between both shoes.
| Fanning W (US) | Internal Cavity | Reef Neptune Equivalent | Match Accuracy | Fit Difference |
|---|---|---|---|---|
| US 3.5 | 240 mm | US 3.5 | 53% | +4.0 mm |
| US 4 | 243 mm | US 3.5 | 88% | +1.0 mm |
| US 4.5 | 247 mm | US 4 | 100% | 0.0 mm |
| US 5 | 250 mm | US 4.5 | 88% | +1.0 mm |
| US 5.5 | 253 mm | US 5 | 88% | +1.0 mm |
| US 6 | 257 mm | US 5.5 | 100% | 0.0 mm |
| US 6.5 | 260 mm | US 6 | 88% | +1.0 mm |
| US 7 | 267 mm | US 6.5 | 65% | -3.0 mm |
| US 7.5 | 270 mm | US 7 | 88% | +1.0 mm |
| US 8 | 273 mm | US 7.5 | 88% | +1.0 mm |
| US 8.5 | 277 mm | US 8 | 100% | 0.0 mm |
| US 9 | 280 mm | US 8.5 | 88% | +1.0 mm |
| US 9.5 | 283 mm | US 9 | 88% | +1.0 mm |
| US 10 | 287 mm | US 9.5 | 100% | 0.0 mm |
| US 10.5 | 290 mm | US 10 | 88% | +1.0 mm |
| US 11 | 293 mm | US 10.5 | 88% | +1.0 mm |
| US 11.5 | 297 mm | US 11 | 100% | 0.0 mm |
| US 12 | 300 mm | US 11.5 | 88% | +1.0 mm |
| US 12.5 | 303 mm | US 12 | 88% | +1.0 mm |
| US 13 | 307 mm | US 12.5 | 100% | 0.0 mm |
| US 14 | 313 mm | US 13 | 76% | -2.0 mm |
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Frequently Asked Questions
How does the Fanning W size compare to the Reef Neptune?
The Reef Neptune provides about 4mm more internal length than the Fanning W. We suggest ordering 1/2 size down in Reef Neptune. The Fanning W has an internal fit offset of 0mm compared to 4mm for the Reef Neptune.
Do these shoes fit wide feet comfortably?
The Fanning W has a standard medium width profile, while the Reef Neptune is standard medium.