C series of ISO paper sizes

The C Series are envelope sizes designed to fit A series sheets of paper. See also envelope sizes in Europe.

Size	Dimensions in mm	Fits
C0	917 by 1297
C1	648 by 917
C2	458 by 648
C3	324 by 458
C4	229 by 324	an A4 sheet, not folded
C5	162 by 229	an A4 sheet folded in half; an A5 sheet, not folded
C6	114 by 162	an A4 sheet folded in quarters; an A5 sheet folded in half; an A6 sheet, not folded
C7	81 by 114
C8	57 by 81
C9	40 by 57
C10	28 by 40