Envelope Sizes

C Series

The C series is used for postcards, folders and envelopes. Each C size envelope or folder will take the corresponding A size letter inside it without folding. For example, a C5 envelope is suitable for posting an A5 letter unfolded, or an A4 letter folded in half.

ISO International Standard Envelope Sizes

 

Size

Dimension

Takes letter…

C3

324 x 458

A3 unfolded

B4

250 x 353

A4 unfolded

C4

229 x 324

A4 unfolded

B5

176 x 250

A5 unfolded or A4 folded in half

C5

162 x 229

A5 unfolded or A4 folded in half

B6/C4

324 x 176

A4 folded in half lengthwise

B6

125 x 176

A6 unfolded or A5 folded in half

C6

114 x 162

A6 unfolded or A5 folded in half

DL

110 x 220

A4 folded in thirds

C7/6

81 x 162

A5 folded in thirds

C7

81 x 114

A7 unfolded or A6 folded in half