True-to-Size Millimeter Sizing Comparison
Allbirds Wool Runner vs ASICS GEL-Nimbus 27
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 Wool Runner to see your calculated size in the GEL-Nimbus 27.
Complete Size Conversion Matrix
Direct millimeter-calibrated mapping comparing all available sizes between both shoes.
| Wool Runner (US) | Internal Cavity | GEL-Nimbus 27 Equivalent | Match Accuracy | Fit Difference |
|---|---|---|---|---|
| US 3.5 | 239 mm | US 4 | 81% | +1.6 mm |
| US 4 | 242 mm | US 4.5 | 57% | +3.6 mm |
| US 4.5 | 246 mm | US 4.5 | 95% | -0.4 mm |
| US 5 | 249 mm | US 5 | 81% | +1.6 mm |
| US 5.5 | 252 mm | US 5.5 | 57% | +3.6 mm |
| US 6 | 256 mm | US 5.5 | 95% | -0.4 mm |
| US 6.5 | 259 mm | US 6 | 81% | +1.6 mm |
| US 7 | 266 mm | US 7 | 75% | +2.1 mm |
| US 7.5 | 269 mm | US 7.5 | 81% | +1.6 mm |
| US 8 | 272 mm | US 8 | 57% | +3.6 mm |
| US 8.5 | 276 mm | US 8 | 95% | -0.4 mm |
| US 9 | 279 mm | US 8.5 | 81% | +1.6 mm |
| US 9.5 | 282 mm | US 9 | 57% | +3.6 mm |
| US 10 | 286 mm | US 9 | 95% | -0.4 mm |
| US 10.5 | 289 mm | US 9.5 | 81% | +1.6 mm |
| US 11 | 292 mm | US 10 | 57% | +3.6 mm |
| US 11.5 | 296 mm | US 10.5 | 75% | +2.1 mm |
| US 12 | 299 mm | US 11 | 81% | +1.6 mm |
| US 12.5 | 302 mm | US 11.5 | 57% | +3.6 mm |
| US 13 | 306 mm | US 11.5 | 95% | -0.4 mm |
| US 14 | 312 mm | US 12.5 | 57% | +3.6 mm |
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Frequently Asked Questions
How does the Wool Runner size compare to the GEL-Nimbus 27?
Both shoes share a very similar length profile. We recommend ordering your standard size in both. The Wool Runner has an internal fit offset of -0.68mm compared to -0.08mm for the GEL-Nimbus 27.
Do these shoes fit wide feet comfortably?
The Wool Runner has a standard medium width profile, while the GEL-Nimbus 27 is snug/narrow.