Start with the open door
Open the door through its full swing. Watch where the door and handle travel, then check the space you use to walk through. Measure from the wall to the nearer edge of the door swing or walking path. Start at any trim or baseboard that keeps a rack from sitting against the wall. Take a second measurement if the space narrows.
Try one thing you already own
Set a tray or low basket outside the door’s path and use it only for the shoes you wear most. Put keys in a dish on an existing surface. If bags stick out past the basket or leave you stepping around them, give the bags a spot elsewhere. Open the door and walk through with a bag in your hand before deciding whether the setup works.
Check how a cabinet opens
IKEA lists the white TRONES shoe cabinet, item 003.973.07, at 7⅛ inches deep and requires it to be secured to the wall. That listed depth is one measurement. Check the space a cabinet takes with its front open before you buy. If you can’t attach a cabinet as its maker requires, use another option.
Write down the limits before shopping
Record the maximum depth and width available outside the door’s path. Add the space you need to open the proposed storage. Bring that note with you so you can rule out pieces that look small but take more space in use.