A Complete Guide to Envelope Types and Sizes

Envelopes are an essential part of any office stationery collection. These humble yet indispensable tools protect documents, ensure confidentiality, and make the transport of important materials simple and professional.

But do you know the difference between a C5 and a DL envelope? If not, don’t worry as we’ve created a comprehensive guide to help you select the perfect envelope for your needs.

Though it may seem like an envelope is just an envelope, the type you choose should depend on the contents you’re sending. Let’s explore the different envelope types, their common uses, and why keeping a variety on hand is always a good idea.

C4 Envelopes

• Size: 324 x 229 mm (12.76 x 9.02 inches)
• Ideal for: A4 sized documents
• Common uses: Certificates, brochures, magazines, and documents that need to remain flat
• Description: C4 envelopes are slightly larger than an A4 sheet, making them perfect for sending documents without folding. They’re a must-have in any office for formal or professional mailings.

C5 Envelopes

• Size: 229 x 162 mm (9.02 x 6.38 inches)
• Ideal for: A4 paper folded in half
• Common uses: Greeting cards, invitations, and longer letters
• Description: This traditional-sized envelope is larger than A5 but designed to snugly fit an A4 sheet folded once. It’s popular for sending wedding invitations, formal correspondence, or documents requiring extra space.

C6 Envelopes

• Size: 162 x 114 mm (4.92 x 6.89 inches)
• Ideal for: A6-sized items, small documents, A5 paper folded once
• Common uses: A5 writing paper folded in half, invitations or postcards
• Description: The smallest size in many stationery collections, C6 envelopes are perfect for mailing compact items. While they’re less commonly seen in mailboxes, they’re handy to have for specific situations.

125 x 175 Envelopes

• Size: 125 x 175 mm (8.67 x 8.67 inches)
• Ideal for: Greeting cards, large postcards, invitations
• Common uses: Greeting cards, wedding invitations, and larger postcards
• Description: Slightly larger than C6 envelopes, 125 x 175 envelopes are a versatile option for smaller items. They are ideal for casual and creative communications like postcards or invitations, offering a clean, tailored look. While not as widely used as standard business envelopes, their size adds a personal touch to any correspondence, making them handy for special occasions or artistic projects.

DL Envelopes

• Size: 220 x 110 mm (8.67 x 4.33 inches)
• Ideal for: A4 paper folded in thirds
• Common uses: Business letters and official correspondence
• Description: DL envelopes are a staple in professional environments. They’re designed for one to three-page letters and often feature a transparent window to display recipient details without additional labelling.

DL+ Envelopes

• Size: 229 x 114 mm (9.02 x 4.49 inches)
• Ideal for: A4 paper folded in thirds with extra room
• Common uses: Business correspondence requiring more capacity than standard DL envelopes
• Description: These slightly larger envelopes provide extra space while maintaining the familiar shape of DL envelopes, making them ideal for thicker letters or documents.

Square Envelopes

• Size: 220 x 220 mm (8.67 x 8.67 inches)
• Ideal for: Square-shaped documents
• Common uses: Greeting cards, wedding invitations, and specialty mailings
• Description: With their unique shape, square envelopes are less common but perfect for special occasions. They add a touch of elegance and creativity to any mail.