Leaflet / brochure sizes

The most common mistake with a tri-fold leaflet is splitting the sheet into three equal panels. In a roll fold (letter fold), the innermost panel tucks inside the other two, so it must be slightly narrower or it buckles against the fold. On US Letter (11 × 8.5 in) the panels are 3.6875, 3.6875 and 3.625 in — the tuck-in panel is 1/16 in narrower. On A4 the usual split is 100, 100 and 97 mm.

A Z-fold (accordion) is different: no panel tucks inside another, so all three panels are equal. A gate fold, where two outer flaps meet in the middle, makes each flap about 2 mm narrower than half the centre panel. Choose the fold before you design, because the panel widths — and therefore the whole grid — follow from it.

Keep text and key parts of photos off the fold lines, and give each panel its own inner margin rather than treating the flat sheet as one page. A bi-fold (a sheet folded once) is the simplest case: two equal halves, such as A3 folded to A4.