What size envelope for A5?
A5 fits a C5 envelope flat, a C6 folded once, and a DL folded in three.
Smallest envelope for each fold
A5 is 148 × 210 mm, the size of a half-sheet of A4 or a medium notebook page.
| Fold | Size of folded sheet | Smallest envelope | Envelope size | Spare (width, length) | Next sizes up |
|---|---|---|---|---|---|
| flat | 148 × 210 mm | US A10 (Willow) | 152.4 × 241.3 mm | 4.4 × 31.3 mm | C5, C4 |
| folded in half | 148 × 105 mm | C6 | 114 × 162 mm | 9 × 14 mm | US A6 (Thompson), DL, US A7 (Besselheim) |
| folded in three (letter fold) | 148 × 70 mm | C6 | 114 × 162 mm | 44 × 14 mm | US No. 7 3/4 (Monarch), US A6 (Thompson), US No. 9 |
| folded in quarters | 74 × 105 mm | US A2 (Lady Grey) | 111.1 × 146 mm | 37.1 × 41 mm | C6, US No. 7 3/4 (Monarch), US A6 (Thompson) |
At least 3 mm spare each way is required. Computed from the dimensions of ISO C and DL envelopes and the US sizes on the envelope sizes page.
Every envelope tested
Spare room in mm (width × length) for each fold; a dash means it does not fit.
| Envelope | Size (mm) | Flat | Half | Thirds | Quarters |
|---|---|---|---|---|---|
| DL | 110 × 220 | – | 5 × 72 | 40 × 72 | 36 × 115 |
| C6 | 114 × 162 | – | 9 × 14 | 44 × 14 | 40 × 57 |
| C6/C5 | 114 × 229 | – | 9 × 81 | 44 × 81 | 40 × 124 |
| C5 | 162 × 229 | 14 × 19 | 57 × 81 | 92 × 81 | 88 × 124 |
| C4 | 229 × 324 | 81 × 114 | 124 × 176 | 159 × 176 | 155 × 219 |
| US No. 7 3/4 (Monarch) | 98 × 190 | – | – | 28 × 42 | 24 × 86 |
| US No. 9 | 98 × 225 | – | – | 28 × 77 | 24 × 120 |
| US No. 10 (Business) | 105 × 241 | – | – | 35 × 93 | 31 × 136 |
| US No. 11 | 114 × 264 | – | 9 × 116 | 44 × 116 | 40 × 159 |
| US No. 12 | 121 × 279 | – | 16 × 131 | 51 × 131 | 47 × 174 |
| US No. 14 | 127 × 292 | – | 22 × 144 | 57 × 144 | 53 × 187 |
| US A2 (Lady Grey) | 111 × 146 | – | – | – | 37 × 41 |
| US A6 (Thompson) | 121 × 165 | – | 16 × 17 | 51 × 17 | 47 × 60 |
| US A7 (Besselheim) | 133 × 184 | – | 28 × 36 | 63 × 36 | 59 × 79 |
| US A8 (Carrs) | 140 × 206 | – | 35 × 58 | 70 × 58 | 66 × 101 |
| US A9 (Diplomat) | 146 × 222 | – | 41 × 74 | 76 × 74 | 72 × 117 |
| US A10 (Willow) | 152 × 241 | 4 × 31 | 47 × 93 | 82 × 93 | 78 × 136 |
Which one to pick
The C5 envelope (162 × 229 mm) is the ISO match for A5 flat. If you fold A5 in half it becomes A6 and goes in a C6 envelope, which is the usual route for a note or a greeting card. An A5 sheet folded in three is 70 × 210 mm and fits a DL with plenty of spare width; note that DL is built for A4 in thirds, so an A5 folded this way rattles around. See C5 and C6.
Frequently asked questions
What size envelope do I need for A5?
C5 (162 x 229 mm) for flat A5, C6 (114 x 162 mm) for A5 folded once, DL for A5 folded in three.
Does A5 fit in a DL envelope?
Only if folded. A5 flat is 148 mm wide and a DL is 110 mm. Folded in three the sheet is 70 x 210 mm and fits.
Does A5 fit in a C6 envelope?
Folded in half, yes: it becomes A6 (105 x 148 mm) with 9 mm and 14 mm spare.