C5 envelope size and dimensions
A C5 envelope measures 162 × 229 mm, which is 16.2 × 22.9 cm or 6.4 × 9 inches. It takes A5 flat or A4 folded once. With Royal Mail it still counts as a Letter, while in Germany it is always a Großbrief.
Contents of this page
C5 envelope, portrait
162 × 229mm
- Centimetres
- 16.2 × 22.9 cm
- Inches
- 6.38 × 9.02 in
- Pixels at 300 dpi
- 1913 × 2705 px
- Points (pt)
- 459 × 649 pt
- Area
- 0.0371 m²
- Weight at 80 gsm
- 2.97 g
C5 is the envelope for booklets, brochures, A5 greeting cards and letters you only want to fold once. Postage is where it gets interesting, because the UK and Germany treat it quite differently.
C5 in every unit
| Unit | Width × height |
|---|---|
| Millimetres | 162 × 229 mm |
| Centimetres | 16.2 × 22.9 cm |
| Metres | 0.162 × 0.229 m |
| Inches | 6.38 × 9.02 in |
| DTP points (1/72 in) | 459 × 649 pt |
| Area | 371 cm², or 0.0371 m² |
| Diagonal | 280.5 mm |
| Aspect ratio | 1 : 1.414 |
What fits in a C5 envelope
| Contents | Size | Room around it |
|---|---|---|
| A5 flat | 148 × 210 mm | 7 mm at the sides, 9.5 mm top and bottom |
| A4 folded once | 148.5 × 210 mm | as for A5 |
| A5 folded card | 148 × 210 mm folded | as for A5, watch the thickness |
| C6 envelope | 114 × 162 mm | plenty, for a reply envelope |
Postage in the UK and Germany
Royal Mail: a Letter may be up to 240 × 165 mm, 5 mm thick and 100 g. C5 is 162 mm tall, so it just fits and goes at the cheaper Letter rate, as long as it stays thin.
Deutsche Post: a standard letter (Standardbrief) and a Kompaktbrief may be no more than 125 mm tall. C5 is too tall for both and always goes as a Großbrief, which costs €1.80 in 2026 for up to 500 g. Folding A4 in three and using a DL envelope brings the price down to €0.95.
C5 window envelopes
C5 envelopes with a window are made for letters folded once down the middle. The window is usually 90 × 45 mm and sits 20 mm from the left edge. Its height varies more than on DL envelopes, so test a letter before ordering in bulk. How address and window line up is explained on window envelopes.
Frequently asked questions
How big is a C5 envelope?
162 × 229 mm, which is 16.2 × 22.9 cm or about 6.4 × 9 inches.
What fits in a C5 envelope?
A5 flat, A4 folded once, A5 cards and booklets, and a C6 envelope.
Is a C5 envelope a Large Letter?
Not with Royal Mail, as long as it is no more than 5 mm thick and 100 g. At 162 mm tall it stays within the 165 mm Letter limit.
Is a C5 envelope a standard letter in Germany?
No. Deutsche Post allows at most 125 mm for a Standardbrief, so C5 goes as a Großbrief.