What is the C Series?
The C Series is a standard for envelope sizes defined by ISO 269. It is designed to hold A Series paper without folding. C Series envelopes are the professional choice for business mail, invitations, and official correspondence worldwide.
Geometric Mean
The C Series is based on the geometric mean of the A and B Series. This ensures C Series envelopes perfectly fit A Series paper with minimal waste.
Standardized Sizes
C0 to C8 and DL are defined in ISO 269. Each size holds the corresponding A Series size: C4 holds A4, C5 holds A5, and so on.
Global Standard
The C Series is used worldwide for professional mail, invitations, and business correspondence. It ensures compatibility across international borders.
C Series Envelope Sizes
Complete reference for all C Series envelope sizes with dimensions and what paper they hold.
๐ Complete C Series Size Table
Detailed comparison of all C Series envelope sizes with A Series equivalents.
| Size | mm | inches | Holds | Common Use |
|---|---|---|---|---|
| C0 | 917 ร 1297 | 36.1 ร 51.1 | A0 | Very large displays, posters |
| C1 | 648 ร 917 | 25.5 ร 36.1 | A1 | Large posters, presentations |
| C2 | 458 ร 648 | 18.0 ร 25.5 | A2 | Oversized mail, catalogs |
| C3 | 324 ร 458 | 12.8 ร 18.0 | A3 | Large catalogs, invitations |
| C4 | 229 ร 324 | 9.0 ร 12.8 | A4 | Standard business envelopes |
| C5 | 162 ร 229 | 6.4 ร 9.0 | A5 | Invitations, flyers |
| C6 | 114 ร 162 | 4.5 ร 6.4 | A6 | Greeting cards, invitations |
| C7 | 81 ร 114 | 3.2 ร 4.5 | A7 | Small cards, tags |
| C8 | 57 ร 81 | 2.2 ร 3.2 | A8 | Very small notes, labels |
| DL | 110 ร 220 | 4.3 ร 8.7 | A4 folded | Business mail, invoices |
โ๏ธ C Series Envelope Uses
Business Correspondence
C4 envelopes are the standard for business mail, official documents, and professional correspondence. They hold A4 paper without folding, ensuring documents arrive pristine.
Invitations & Cards
C5 and C6 envelopes are popular for invitations, greeting cards, and personal correspondence. They offer a professional presentation for important communications.
Direct Mail
DL envelopes are the most common for business mail, invoices, and marketing materials. They are designed to hold A4 paper folded in thirds, making them cost-effective for bulk mail.
Creative Projects
C Series envelopes are used by designers and artists for portfolios, art prints, and creative projects. The standardized sizes ensure compatibility with A Series paper.
Professional Printing
Printers use C Series envelopes for professional print jobs. The sizes ensure documents fit perfectly without trimming or waste.
International Mail
C Series is recognized globally, making it ideal for international correspondence. Your mail will look professional in any country.
๐ก Professional Tips for C Series Envelopes
๐ฏ Choosing the Right Size
Always choose an envelope that matches your paper size without folding. For A4 documents, use C4. For folded A4 (DL), use DL envelopes. This ensures professional presentation and reduces damage during mailing.
๐ Quality Matters
Invest in high-quality envelopes with proper gussets and flaps. Professional envelopes make a lasting impression on clients and business partners.
๐จ๏ธ Printing Compatibility
Ensure your printer supports C Series envelope sizes. Check your printer's specifications before ordering large quantities.
๐ฌ Mailing Regulations
Check with your postal service for weight and size restrictions. C Series envelopes are designed to meet international mailing standards.
โป๏ธ Sustainability
Choose recycled or sustainably sourced envelopes where possible. Many C Series envelopes are available with FSC certification.