C4 envelope size and dimensions
A C4 envelope measures 229 × 324 mm, which is 22.9 × 32.4 cm or 9 × 12.75 inches. It is made for A4: the sheet goes in flat, with just under 1 cm to spare on each side and a good 1.3 cm at the top and bottom.
Contents of this page
C4 envelope, portrait
229 × 324mm
- Centimetres
- 22.9 × 32.4 cm
- Inches
- 9.02 × 12.76 in
- Pixels at 300 dpi
- 2705 × 3827 px
- Points (pt)
- 649 × 918 pt
- Area
- 0.0742 m²
- Weight at 80 gsm
- 5.94 g
C4 is the envelope for anything that must not be folded: certificates, contracts, CVs, photos and A4 brochures. With Royal Mail it goes as a Large Letter, in Germany as a Großbrief or, if heavy or thick, a Maxibrief.
C4 in every unit
| Unit | Width × height |
|---|---|
| Millimetres | 229 × 324 mm |
| Centimetres | 22.9 × 32.4 cm |
| Metres | 0.229 × 0.324 m |
| Inches | 9.02 × 12.76 in |
| DTP points (1/72 in) | 649 × 918 pt |
| Area | 742 cm², or 0.0742 m² |
| Diagonal | 396.8 mm |
| Aspect ratio | 1 : 1.415 |
What fits in a C4 envelope
| Contents | Size | Fits? |
|---|---|---|
| A4 flat | 210 × 297 mm | yes, the normal case |
| A4 booklet or brochure | 210 × 297 mm, a few mm thick | yes, use a gusset envelope for thicker ones |
| C5 envelope | 162 × 229 mm | yes, for a reply envelope, for example |
| A4 clip file | about 240 × 305 mm | no, use B4 |
| US Letter | 215.9 × 279.4 mm | yes |
Types of C4 envelope
- Window or plain: the window is usually 90 × 45 or 90 × 55 mm and sits 20 mm from the left edge, positioned for an unfolded letter. The height varies between makers, so test one letter first.
- Board-backed: a sheet of board keeps certificates and photos flat. They often say “Please do not bend”.
- Gusset with base: for catalogues and thick documents. The envelope opens out and takes several centimetres of contents.
- Closure: peel and seal is the most convenient, self-seal and gummed are cheaper.
Postage and weight
| Service | Weight | Thickness |
|---|---|---|
| Royal Mail Large Letter | up to 750 g | up to 25 mm |
| Deutsche Post Großbrief (2026) | up to 500 g | up to 20 mm |
| Deutsche Post Maxibrief (2026) | up to 1000 g | up to 50 mm |
A C4 envelope weighs roughly 15 to 20 g depending on the paper. With 80 g/m² copy paper, about 95 sheets fit into a German Großbrief before the 500 g limit. Deutsche Post has announced new limits for 2027, with the Großbrief allowed up to 1000 g and 30 mm. Details on German letter sizes.
Frequently asked questions
How big is a C4 envelope?
229 × 324 mm, which is 22.9 × 32.4 cm or about 9 × 12.75 inches.
Does A4 fit in a C4 envelope?
Yes, flat. There is just under 1 cm to spare on each side and a good 1.3 cm at the top and bottom.
Is a C4 envelope a Large Letter?
Yes, with Royal Mail it is a Large Letter up to 750 g and 25 mm thick.
How many sheets fit in a C4 envelope?
By weight, about 95 sheets of 80 g/m² paper stay within a 500 g German Großbrief. Royal Mail allows up to 750 g.
Which envelope is bigger than C4?
B4 at 250 × 353 mm. It takes a C4 envelope or thick A4 documents.