Documents Enclosed Envelopes: Sizes & Where to Buy

Choosing the Right Envelope for Your Documents

Documents enclosed envelopes follow the ISO 216 paper standard, which means each size is built to match a specific paper format without wasted space or awkward folds. The four you will see most often are DL, C6, C5, and C4, ranging from a slim tri-fold letter envelope up to one that carries a full A4 sheet completely flat.

Matching the envelope to the document keeps your mailing professional and avoids unnecessary postage costs on oversized packaging. Globe Packaging stocks all four sizes in white and manilla, with plain, window, self-seal, and peel-and-seal options available in bulk. Orders placed by 4 pm ship the same day from our UK depot.

The Most Common Sizes of Documents Enclosed Envelopes

DL Size (110 x 220mm)

The DL envelope is slim, professional, and fits neatly through most letterboxes.

The DL envelope, short for "Dimension Lengthwise,"  is the most widely used in business correspondence. It measures 110 x 220mm and is designed to hold a standard A4 sheet that has been folded into thirds. This is the classic business letter envelope you see used for invoices, statements, and formal letters every day. 

Best For:

• Standard business letters and correspondence.

• Invoices and payment reminders.

• Folded A4 documents (tri-fold).

• Reply envelopes included inside larger mailings.

C6 Size (114 x 162mm)

The C6 envelope is best for greeting cards, not for bulky documents.  

The C6 envelope measures 114 x 162mm and is the smallest of the four standard sizes. It holds an A4 sheet folded into quarters, or a flat A6-sized card. It's commonly used for greeting cards, invitations, and short notes rather than heavy document mailing.

While not the typical choice for professional document enclosures, C6 envelopes can be useful for sending smaller inserts, promotional cards, or compliment slips alongside a primary mailing.

Best For:

• Greeting cards and invitations.

• Compliment slips.

• A4 documents folded into quarters.

• Short personal or informal correspondence.

C5 Size (162 x 229mm)

C5 envelopes are often used in professional settings and are great for medical or legal correspondence.

The C5 envelope measures 162 x 229mm and is one of the most versatile sizes available. It fits an A4 sheet folded once in half, or a flat A5 document without any folding at all. This makes it a popular choice for businesses that send multi-page letters, small booklets, or documents that shouldn't be tri-folded.

C5 envelopes are large enough to carry meaningful document sets without the bulk of a full C4, and they still fit comfortably through standard letterboxes. Available in both plain white and manilla brown from Globe Packaging, they're a reliable staple for regular office use.

Best For:

• A4 documents folded once in half.

• Flat A5 documents and booklets.

• Multi-page letters and reports.

• Brochures and marketing inserts.

• Medical or legal correspondence that shouldn't be tri-folded.

C4 Size (229 x 324mm)

C4 envelopes are best for contracts, certificates, architectural drawings, and legal documents.

The C4 envelope measures 229 x 324mm, large enough to hold a complete A4 sheet completely flat with no folding required. This is the gold standard for professional document mailing, especially when the contents must arrive uncreased and in pristine condition. 

C4 envelopes are also available in window format, which is especially useful when mailing documents that already include a visible address block. This removes the need to separately address the envelope and reduces the chance of mismatched recipient details.

Best For:

• Full A4 documents sent flat and unfolded.

• Contracts, legal documents, and certificates.

• Multiple-page document packs.

• Presentations and formal proposals.

• Any document where fold lines are unacceptable.

Where to Buy Documents Enclosed Envelopes in Bulk

For businesses that send documents regularly, buying envelopes in bulk is the most cost-effective approach. Purchasing in larger quantities typically reduces the cost per unit, ensures you never run out mid-mailing, and keeps your office running without unnecessary interruptions. 

At Globe Packaging, we offer all four standard sizes in both white and manilla options, with plain and window variations available depending on your mailing needs.

Whether you need self-seal or peel-and-seal closures, plain or window-faced envelopes, or white versus manilla finishes, ordering in bulk from a dedicated supplier means you get consistency across every mailing. 

Documents Enclosed Envelopes: Summary Table

Get Your Documents Enclosed Envelopes from Globe Packaging

The right envelope depends on how you want your documents to arrive. At Globe Packaging, we stock all four standard sizes across white and manilla finishes, with self-seal, peel-and-seal, and window variations to suit different mailing needs. 

We offer free next-working-day delivery on UK mainland orders over £50 (exc VAT), which means you can reorder with confidence and avoid running short mid-mailing. Shop Globe Packaging now. 

*Note: Product listings, prices, and delivery times shown are approximate and subject to change. Contact Globe Packaging for the latest information.