Key findings
What stops a fit, in four lines.
- Across every kind of space, walkway was the single most common binding constraint, deciding 395 checks.
- The next most common blockers were width (228 checks) and height (169 checks).
- The blocker changes with the space: in rooms it is usually walkway clearance, while through openings it is width.
- When something does not fit, it is almost always one measurement, not the whole item, that decides it.
The usual suspects
The blockers that come up most.
Each check that did not fit has one binding constraint, the single measurement that decided it. Here are the three most common.
Across all checks
The binding constraint, ranked.
- walkway395 checks
- width228 checks
- height169 checks
- hallway_width71 checks
- stair_width60 checks
- floor_area48 checks
- no_orientation_fits41 checks
- landing_turn36 checks
- complex_packing_required30 checks
- length30 checks
- elevator_door27 checks
- stair_headroom22 checks
By space type
The blocker changes with the space.
- stairslanding_turnn=36
- roomwalkwayn=331
- openingwidthn=115
- elevatorelevator_doorn=27
- passagewidthn=59
- hallwayhallway_widthn=63
- containerwidthn=48
Methodology
How we counted this.
The binding constraint recorded on each solver verdict that named one, over the data window.
- 01Window: 2026-03-09 to 2026-06-21
- 02Source: the fit_check_results corpus, which carries an account and session identity, so internal QA traffic is removed at the source. The binding constraint is what the solver itself determined to be the tightest limiting measurement, not a guess.
- 03Dimensions: each check uses what the visitor entered. When an item is named without exact measurements, ItemFits fills in typical dimensions before solving (from a product catalog, a saved or web-search lookup, or a model estimate), so these outcomes reflect real-world queries against typical item sizes rather than lab-measured objects.
- 04In the 3033 checks that recorded how the item dimensions were obtained, 36.8% used measurements the visitor supplied. The rest used a size ItemFits resolved for the named item: 38.4% from a known-product match, 4.1% from a web or model estimate, and 20.7% from a default or unspecified source.
The honesty contract
What we excluded.
Every published figure carries its sample size. Anything below the threshold is suppressed, never shown as zero.
- !Internal test accounts, bot sessions, and checks where no single constraint was recorded. Constraint labels that appeared fewer than ten times are suppressed rather than shown.
- !Items are modeled as rigid rectangular boxes (their width by depth by height envelope) and tested across orientations. We do not model irregular shapes, protruding handles or legs, or flexible materials, except where an explicit compression or take-apart allowance applies.
Data last refreshed: June 2026
Cite this study
Use the numbers, link the source.
ItemFits (2026). What Stops Things From Fitting. The most common binding constraint across real fit checks (2026-03-09 to 2026-06-21) was walkway, decisive in 395 checks. https://itemfits.com/data/what-stops-things-fitting
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Frequently asked
Questions we keep getting.
What is a binding constraint?
It is the single measurement that decides a fit check. A couch might clear a doorway on width and height but get stopped by the diagonal at a turn. The turn is the binding constraint.
01Why does the top blocker differ by space?
Each kind of space fails differently. Doorways tend to be stopped by width, stairs by the landing turn and headroom, rooms by floor area. The by-space breakdown shows where each one bites.
02