Definition
What it means.
- Diagonal clearance
- When a flat or boxy item is too tall to slide through a doorway upright, tilting it lets a longer dimension pass along the opening’s diagonal rather than its width. The diagonal clearance is the geometric ceiling on how long that tilted item can be, it is the hypotenuse of the opening rectangle. ItemFits computes it whenever an upright pass fails, to decide whether a tilt rescues the fit.
- Diagonal clearance (32×80 in door)
- 86 in
In depth
The fuller picture.
Trading height for reach
When an item is too tall to slide through a doorway standing up, tilting it lets a longer dimension travel along the opening on the diagonal instead of fighting the width. The diagonal clearance is the geometric ceiling on that move: it is the hypotenuse of the opening rectangle, the straight line from one corner to the opposite corner. A 32 inch wide by 80 inch tall doorway has a diagonal of about 86 inches, which is why an 84 inch sofa that fails upright can still pass when it is leaned.
The diagonal is an upper bound, not a promise. It assumes a thin item, so a piece with real depth uses up part of that diagonal and clears less than the raw hypotenuse suggests. ItemFits computes the diagonal whenever an upright pass fails and then accounts for the item depth, rather than treating the corner-to-corner distance as the whole answer.
Measure it
How to measure.
In practice
How it shows up.
A 32-in-wide × 80-in-tall doorway has a diagonal clearance of about 86 in, which is why an 84-in sofa often passes only when tilted.
How it is computed
The math behind it.
√(w² + h²)√(32² + 80²) ≈ 86 in for a 32″×80″ door.
Go deeper
Related terms and tools.
Frequently asked
Questions we keep getting.
Is diagonal clearance the same as the door’s diagonal?
Yes, it is the straight-line distance across the opening corner to corner.
01Why can an item longer than the door still pass?
Because tilting it lets the length ride the opening on the diagonal, which is longer than either the width or the height alone.
02Does item depth change the diagonal clearance?
The diagonal of the opening is fixed, but a deeper item consumes more of it, so the usable diagonal for a real piece is less than the bare hypotenuse.
03