Standard envelope formats

• C4 – 324 x 229 mm
• C5 – 229 x 162 mm
• C6 – 162 x 114 mm
• EA4 – 312 x 220 mm
• EA5 – 200 x 156 mm
• EA5/6 – 220 x 110 mm
• EA6 – 156 x 110 mm

If you only want to send an A4 letter unfolded then choose a C4 envelope. If you want to send the A4 letter folded 1 turn, it goes in an EA5 envelope. A 2 turn folded A4 letter is sent in an EA5/6 envelope.