Moving Sofa Constant

Upper bound, last-listed row

| 2.2195* | [Baek2024] | Announced (unverified) bound, matching the Gerver construction |bound cell edited 2026-09-05

Lower bound, last-listed row

| 2.2195 | [Gerver1992] | The Gerver sofa |tracked since 2026-07-24 — no movement seen yet

Checked against material for its cited source

• Another row, not one shown above: bound row $2 \sqrt{2}$ line 13 citing [Hammersley1968] — the claim we checked: that Hammersley's 1968 article gives the upper bound 2√2 for the moving sofa's area at the place the reference names (Appendix IV, Problems, Problem 8, p. 84). What we read supports it. This verdict does not cover any later paper's quotation of 2√2, which was not used in place of the article. source link (read in the cited Bulletin printing, as a scan a third party uploaded to the Internet Archive (printed pp. 66–85; not a publisher-hosted copy): Problem 8 on p. 84, read from the page image. The article sets "Prove that A<2√2" as an exercise for its readers and gives no proof of it. The publication volume and year are not printed on the pages read. The PDF's embedded keywords give volume 4 and 1968; the Internet Archive item record also gives 1968). Selected: drawn by its position in the list of cited rows, not because it looked wrong.

1 bound row(s) here have been checked against material for their cited source (1 drawn by position, 0 chosen because something already looked wrong). Across this whole ledger 70 row(s) have been drawn by position, against 691 rows that name a source, counted on 2026-09-27: 64 were checked against material for their cited sources and for 6 the cited source could not be read at all. 5 more were chosen for suspicion and checked; they are counted apart, because a set selected for suspicion carries no rate. A row not listed here has NOT been checked.