Plan for a long wall, then measure.
If the reported 27 mm face width is accurate, 19 tiles span about 20.2 inches before extra room. That is longer than an 18-inch rack.
This is arithmetic from an owner-reported size. It does not confirm the dimensions of every Costco set or the usable ledge of a particular rack.
What owners have reported.
In one Costco thread, an owner reported tiles about 37 mm tall and 27 mm wide, with no mat: tiles, three dice, a carrying case, and plastic storage boxes. In another thread, an owner reported ten jokers and four blanks, and said racks about 18 inches long held only 17 tiles across. Those are separate owner reports, not one verified contents list or a statement about current stock.
Before ordering or reusing a rack, read the current package contents and measure a tile across the face. If you know the usable rack ledge, enter both measurements in the rack fit calculator.
Owner discussions: tile size and contents, jokers, blanks, and an 18-inch rack, and rack length. Costco’s product listing could not be checked for this guide, so the dimensions and contents remain owner-reported.
Does the box include a mat?
The owners cited above did not report a mat in the set they discussed. Check the exact package before treating a mat as included. If you have one, measure it and the usable tabletop with the mat fit calculator.
Can you use the tiles for American play?
The owner reports do not give a full tile breakdown. Count suits, winds, dragons, flowers, and jokers with the tile count checker, then ask the host whether the tile faces and extras suit the group.
For other named set checks, see Sam’s Club, Hobby Lobby, Target, and Yellow Mountain Imports.