Key findings
What stops a fit, in four lines.
- Among 627 eligible failed route-related checks, No rotation fits was recorded most often (n=438).
- The next most recorded blockers were Elevator door (n=34) and Stair width (n=29).
- Opening checks formed the largest observed failed-check category (n=454), but this reflects what ItemFits visitors chose to check, not the failure probability of a complete delivery route.
- A stage category is one solver family for one check. ItemFits does not observe an ordered end-to-end move, so this study does not claim which stage usually fails across all deliveries.
The usual suspects
The blockers that come up most.
Each included check failed, belonged to a route-related solver family, and recorded one binding constraint. Here are the three most common.
Across the eligible cohort
The recorded binding constraint, ranked.
- No rotation fits438 failed checks
- Elevator door34 failed checks
- Stair width29 failed checks
- Stair headroom28 failed checks
- Elevator cab depth25 failed checks
- Doorway/opening width20 failed checks
- Available depth20 failed checks
- Opening height11 failed checks
Observed check category
Where visitors ran the failed check.
- opening454 failed checks
- elevator95 failed checks
- stairs71 failed checks
- turn6 failed checks
- hallway1 failed checks
Within each category
The leading recorded constraint by stage category.
- openingNo rotation fits (n=438)cohort n=454; suppressed n=1
- hallwayNo constraint label cleared the publication thresholdcohort n=1; suppressed n=1
- stairsStair width (n=29)cohort n=71; suppressed n=14
- elevatorElevator door (n=34)cohort n=95; suppressed n=6
- turnNo constraint label cleared the publication thresholdcohort n=6; suppressed n=6
Methodology
How we counted this.
One row per failed opening, hallway, stair, elevator, passage, or turn fit check that recorded a binding constraint. The frozen analysis contract is route-blockers/1; eligible n=627.
- 01Window: 2026-07-25 to 2026-09-09
- 02Source: the QA-clean fit_check_results corpus. The binding constraint is the solver-recorded limiting measurement. Stage means the selected solver family for one check, not an observed ordered delivery journey. Results describe ItemFits usage and must not be generalized to all moves or treated as causal failure rates.
- 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 3018 checks that recorded how the item dimensions were obtained, 29.3% used measurements the visitor supplied. The rest used a size ItemFits resolved for the named item: 37.8% from a known-product match, 9.8% from a web or model estimate, and 23.1% 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 and sessions; non-failure outcomes; room, container, vehicle, inventory, and other non-route solver families; and 0 failed route checks with no recorded constraint. Constraint labels with n<10 are suppressed; 22 eligible rows are retained only in the denominator.
- !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: September 2026
Cite this study
Use the numbers, link the source.
ItemFits (2026). What Stops Things From Fitting. Among 627 failed route-related fit checks with a recorded binding constraint (2026-07-25 to 2026-09-09), No rotation fits was recorded in 438 checks. Version route-blockers/1. 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.
01Does this show which stage usually fails during a complete move?
No. Each row is one fit check in one solver family. The study shows the mix among failed checks ItemFits visitors chose to run; it does not observe every stage of an ordered delivery route.
02Why are some constraints missing?
Constraint labels recorded fewer than ten times are suppressed rather than displayed. Their rows remain in the published denominator so the visible shares cannot become false-green.
03