C Series Paper Sizes

The C series paper system is defined by ISO standards and is primarily used for envelopes. Each C size is designed to fit a corresponding A series document, either flat or folded, depending on the size.
Unlike A series paper, which is used for documents, C series sizes include extra space so paper can be inserted without bending or trimming. This makes the C series essential for mailing documents, storing papers, and professional correspondence.

Recommended vs supported structure
C series sizes are designed to sit between A series and B series dimensions. Each C size is slightly larger than the equivalent A size, ensuring documents fit comfortably inside envelopes.
Practical relationship with A series
For example, a C4 envelope fits an A4 document without folding, while a C5 envelope fits an A4 sheet folded once. This consistent relationship makes it easy to match envelopes to document sizes.
Design considerations
When designing envelopes, layouts should account for internal margins and flap areas to prevent content from being obscured or cut off.

Recommended vs supported sizes
C0 envelopes use 10827 × 15319pixels and are the largest standard C series format.
Best practices for visibility
C0 is typically used for large documents, technical drawings, or bulk storage. Designs should focus on clear labeling rather than dense content.
Quality and export considerations
Always export at full resolution and avoid scaling smaller designs up to this size.

Recommended vs supported sizes
C1 envelopes are designed at 7654 × 10827 pixels.
Best practices for visibility
C1 is suitable for large-format documents that must remain flat. Keep text minimal and well-spaced.
Quality and export considerations
Design at final size to preserve clarity and alignment.

Recommended vs supported sizes
C2 envelopes use 5417 × 7654 pixels and are commonly used for posters or large prints.
Best practices for visibility
Use simple layouts and clear labeling, as envelopes are functional rather than decorative.
Quality and export considerations
Export at exact dimensions to ensure proper fit during printing.

Recommended vs supported sizes
C3 envelopes are designed at 3827 × 5417 pixels.
Best practices for visibility
C3 is often used for unfolded A3 documents. Avoid placing content near edges or flap areas.
Quality and export considerations
Maintain generous margins and export at high quality.

Recommended vs supported sizes
C4 envelopes use 2716 × 3827 pixels and fit A4 documents without folding.
Best practices for visibility
This is the most common size for professional correspondence. Address and branding should be placed within safe areas.
Quality and export considerations
Design at the final size and avoid resizing after layout is complete.

Recommended vs supported sizes
C5 envelopes are designed at 1913 × 2716 pixels and fit A4 documents folded once.
Best practices for visibility
Layouts should account for folding direction and window placement if applicable.
Quality and export considerations
Export at exact dimensions to avoid misalignment during printing.

Recommended vs supported sizes
C6 envelopes use 1346 × 1913 pixels and are commonly used for folded A4 or A5 documents.
Best practices for visibility
Because of the smaller size, keep designs simple and text large enough to remain readable.
Quality and export considerations
Avoid scaling down complex designs, as details may be lost.

Recommended vs supported sizes
C7 envelopes are designed at 945 × 1346 pixels and are the smallest standard C series size.
Best practices for visibility
C7 is used for small inserts or cards. Minimal text and bold elements work best.
Quality and export considerations
Export at full resolution to maintain sharp edges and legibility.

• Match C series envelopes to the correct A series document size
• Leave internal margins for flaps and seams
• Avoid placing important content near edges
• Design at the final envelope size
• Export files at high quality for clean printing

Picsart helps you design and resize C series envelopes using exact pixel dimensions, making it easier to prepare files for printing and mailing.
Use the Photo Editor to set a custom canvas size that matches your chosen C series format before designing. This ensures your layout fits the envelope correctly from the start.
If you need to convert an existing design, the Image Resizer allows you to resize layouts to C series dimensions while maintaining proportions.
For documents being inserted into envelopes, referencing A4 poster sizes helps ensure compatibility between document and envelope dimensions.
When preparing final files, exporting as PDF documents preserves layout accuracy. For physical output, Picsart Print helps ensure correct formatting for production.
Always export at the final size and highest quality to avoid scaling issues.