Envelope finder: which envelope fits?
Choose the paper size and the fold. The envelope finder lists every standard envelope your contents fit into, with the room to spare in millimetres. An A4 sheet folded in three, for example, fits a DL envelope with a good 5 mm to spare on every side.
Contents of this page
Envelope finder
| Envelope | mm | Room (W × H) |
|---|
How it is calculated
The calculator first works out the size of the folded contents. Folding once halves the long side, folding in three divides it by three, and folding twice (a cross fold) halves both sides. It then checks each envelope: it fits if at least 3 mm remain on both sides. Less than 6 mm counts as “tight”: the contents catch slightly and machine inserting becomes difficult.
The most common combinations
| Contents | Fold | Envelope |
|---|---|---|
| A4 | unfolded | C4 |
| A4 | once | C5 |
| A4 | in three | DL, C6/5 |
| A4 | twice (cross fold) | C6 |
| A5 | unfolded | C5 |
| A5 | once | C6 |
| A6 | unfolded | C6 |
| Letter | in three | US No. 10, or DL with very little room |
Frequently asked questions
Which envelope fits A4 folded in three?
DL (110 × 220 mm) or C6/5 (114 × 229 mm).
Which envelope fits A5?
C5 for flat A5, C6 for A5 folded once.
Does A4 fit in C5?
Yes, if the sheet is folded once down the middle.