RosaLuxemburgIf it helps ... all four hanwags I have are true to size. My size every time matches perfectly 28,5cm=42EU/9,5US in summer.
For winter I size up for 1/2 size maximum or even not size up at all.
You can measure feet by ruler. There is chart but in cm. Didn't find any in inches.
https://www.bergfreunde.eu/hanwag-size-chart/