True-to-Size Millimeter Sizing Comparison
Allbirds Tree Runner vs Nike Run Swift 3
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 Tree Runner to see your calculated size in the Run Swift 3.
Complete Size Conversion Matrix
Direct millimeter-calibrated mapping comparing all available sizes between both shoes.
| Tree Runner (US) | Internal Cavity | Run Swift 3 Equivalent | Match Accuracy | Fit Difference |
|---|---|---|---|---|
| US 3.5 | 240 mm | US 6 | 97% | -0.3 mm |
| US 4 | 243 mm | US 6.5 | 80% | +1.7 mm |
| US 4.5 | 247 mm | US 7 | 80% | +1.7 mm |
| US 5 | 250 mm | US 7.5 | 68% | +2.7 mm |
| US 5.5 | 253 mm | US 7.5 | 97% | -0.3 mm |
| US 6 | 257 mm | US 8 | 97% | -0.3 mm |
| US 6.5 | 260 mm | US 8.5 | 91% | +0.7 mm |
| US 7 | 267 mm | US 9.5 | 68% | +2.7 mm |
| US 7.5 | 270 mm | US 9.5 | 97% | -0.3 mm |
| US 8 | 273 mm | US 10 | 91% | +0.7 mm |
| US 8.5 | 277 mm | US 10.5 | 91% | +0.7 mm |
| US 9 | 280 mm | US 11 | 68% | +2.7 mm |
| US 9.5 | 283 mm | US 11 | 97% | -0.3 mm |
| US 10 | 287 mm | US 11.5 | 97% | -0.3 mm |
| US 10.5 | 290 mm | US 12 | 91% | +0.7 mm |
| US 11 | 293 mm | US 12.5 | 80% | +1.7 mm |
| US 11.5 | 297 mm | US 13 | 80% | +1.7 mm |
| US 12 | 300 mm | US 13.5 | 56% | +3.7 mm |
| US 12.5 | 303 mm | US 13.5 | 91% | +0.7 mm |
| US 13 | 307 mm | US 14 | 91% | +0.7 mm |
| US 14 | 313 mm | US 15 | 68% | +2.7 mm |
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Frequently Asked Questions
How does the Tree Runner size compare to the Run Swift 3?
Both shoes share a very similar length profile. We recommend ordering your standard size in both. The Tree Runner has an internal fit offset of -0.2mm compared to -0.48mm for the Run Swift 3.
Do these shoes fit wide feet comfortably?
The Tree Runner has a snug/narrow width profile, while the Run Swift 3 is snug/narrow.