Does the KEEN Jasper Zionic Men's run true to size? Should you size up?
We checked, on 8,016 real feet. We worked out the inside measurements of the KEEN Jasper Zionic Men's in the standard width: the length, the width, and the forefoot volume (ball girth). Then we virtually fitted 8,016 real feet from our earlier in-store 3D foot scanners, the way someone shopping online would: KEEN's size chart for length.
KEEN size guide score
56/100
KEEN's size guidance online gave the right size for 56% of 8,016 feet.
Does the KEEN Jasper Zionic Men's run true to size?
For a little over half of feet. If you follow KEEN's size guidance online, the Jasper Zionic Men's fits true to size for 56% of feet. Here, true to size means the size KEEN's online guidance gives you is less than a full size away from the size that fits best, with enough toe room and enough forefoot volume.
KEEN's size guidance gets the length right: KEEN's size chart lists a heel-to-toe foot length for every size, and with that chart, every foot in our fittings had enough room in front of the toes. The guidance falls short on forefoot volume. The Jasper Zionic Men's comes in one width, so a different size is the only way to change the forefoot volume.
Should you size up or down in the KEEN Jasper Zionic Men's?
Here is where every foot landed in the Jasper Zionic Men's when we followed KEEN's size chart.
Following KEEN's size guidance online
- Right size from the size chart56%
- Sized up for more forefoot volume26%
- Sized up for toe room only0%
- Sized down for less forefoot volume18%
Share of 8,016 feet. Each foot is counted once.
- Right size from the size chart: 56% of feet got a size that fit both their foot length and their forefoot volume. KEEN's size chart worked well for this group in the Jasper Zionic Men's.
- Sized up for more forefoot volume: For 26% of feet, the Jasper Zionic Men's had too little forefoot volume at the size the chart gave. The Jasper Zionic Men's has no wide version, so going up a size was the only way to get more forefoot volume, and the bigger size also adds length in front of the toes.
- Sized up for toe room only: No feet landed here: 0 of 8,016. KEEN's size chart leaves every foot enough room in front of the toes in the Jasper Zionic Men's.
- Sized down for less forefoot volume: For 18% of feet, the Jasper Zionic Men's had too much forefoot volume at the size the chart gave. The Jasper Zionic Men's has no narrow version, so a smaller size was the only way to get less forefoot volume, with less room in front of the toes.
How we measured
We measured the standard width of the Jasper Zionic Men's and virtually fitted 8,016 real feet from our earlier in-store 3D foot scanners. Out of 17,311 foot scans, those 8,016 feet fall in the size range of the Jasper Zionic Men's (US men's 7 to 15). For every foot, we followed KEEN's size guidance online: the length chart, in the standard width. A difference of a full size or more between KEEN's size and the size that fits best counts as a miss. These numbers show how the Jasper Zionic Men's fits a large group of feet, not how the shoe feels on your feet.