How do saddle-stitched booklets work and what does 'flat size' vs. 'folded size' mean?

Saddle-stitched booklets are built from full sheets that are printed, folded in half, nested inside one another, and then stapled through the center fold along the spine. Because every sheet folds to create two leaves (four pages), your total page count always comes in multiples of four.

The size confusion usually comes down to two measurements:

• Flat size is the full open sheet before folding. It is roughly double the width of the finished piece.
• Folded (finished) size is the booklet you actually hold after folding and stitching, about half the width of the flat sheet.

Order by the finished size you want, and the flat size is handled during production.