Envelope Size Guide

Choosing the correct envelope size ensures your documents fit perfectly and arrive looking professional. Use the guide below to help you select the right envelope for your mailing.

DL Envelopes (110 × 220 mm)

Best for:

  • Business letters

  • Invoices and statements

  • Everyday business correspondence

What fits inside:

  • A4 paper folded into thirds

Why choose DL envelopes:
DL is the most common envelope size used by UK businesses. It’s ideal for high-volume mail such as invoices, statements, and letters.

Available in window and non-window options.

C5 Envelopes (162 × 229 mm)

Best for:

  • Letters and documents that need more space

  • Brochures and folded leaflets

What fits inside:

  • A4 paper folded in half

  • A5 documents

Why choose C5 envelopes:
C5 envelopes offer a more premium feel and are commonly used for professional communications where presentation matters.

Available in window and non-window options.

C4 Envelopes (229 × 324 mm)

Best for:

  • Contracts and legal documents

  • Certificates and reports

  • Documents that must remain flat

What fits inside:

  • A4 paper without folding

Why choose C4 envelopes:
C4 envelopes are ideal when you need to send important documents without creasing or folding.

Available in window and non-window options.

Window vs Non-Window Envelopes

Window envelopes

  • Ideal for invoices and statements

  • Address shows through the window

  • Reduces the need to print addresses on the envelope

Non-window envelopes

  • Clean, uninterrupted design

  • Ideal for branding and marketing

  • Suitable for hand-written or printed addresses

Need help choosing?

If you’re unsure which envelope size or style is right for your mailing, feel free to contact us at
📧 hello@prosendprint.co.uk

We’re happy to help.