Too tall for the level
The tote's height, including any upright handle or stacking lip, exceeds the vertical opening. On adjustable shelving this is usually the easiest failure to fix — move the shelf. On fixed shelving it means a different tote.
Too deep for the shelf
The tote's depth exceeds the usable depth. This is the least fixable failure: the unit's depth is what it is. A shallower tote is the only remedy.
Too wide in both orientations
An upright rectangular tote can sit two ways round. If neither the width-first nor the depth-first orientation clears the opening, rotating it will not help.
This is worth checking explicitly, because a tote that is too wide one way round often fits the other way.
Fits, but only just
A tote that clears by a very small margin is technically a fit and practically a nuisance: it scrapes, it catches on lips, and it becomes hard to remove when full.
This is what the optional clearance input is for. Add the margin you want to live with and re-check, rather than accepting a bare pass.
Check your own measurements
Re-check with clearance added — the calculator runs entirely in your browser and stores nothing.