Envelope Size Guide


If you’re planning on sending out a mail campaign, you might be wondering what envelope size should I choose?

We’ve created a comprehensive envelope size guide to help you choose the best envelope for the job. Of course, you’ll need an envelope that’s a perfect fit for the letter or brochure it will hold and there are other elements to consider too such as cost of sending and whether the content can be folded.

That’s why we’ve also highlighted some of the most popular sizes with an overview of their common uses. It’s likely your mailer will work in one of these envelopes. However, if your mailer is a little more bespoke there’s a range of alternative ‘C’ envelope sizes available to choose from.

Top tip! An easy way to determine which envelope size you’ll need is to swap the ‘A’ letter of your paper size for the letter ‘C’. For example, A4 paper will fit perfectly inside a C4 envelope. A little caveat to that is the rule doesn’t take in to account folding options.

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Envelope size summary

We’ve popped this handy table below to give you a breakdown of each envelope size and its dimensions in millimetres, centimetres and inches.

 Envelope sizes Size (mm) Size (cm) Size (inches)
C0 917 X 1297 91.7 x 129.7 36.1 x 51.5
C1 648 x 917 64.8 x 91.7 25.5 x 36.1
C2 458 x 648 45.8 x 64.8 18 x 25.5
C3 324 x 458 32.4 x 45.8 12.8 x 18
C4 229 x 324 22.9 x 32.4 9 x 12.8
C5 162 x 229 16.2 x 22.9 6.4 x 9
C6 114 x 162 11.4 x 16.2 4.5 x 6.4
C7 81 x 114 81 x 11.4 3.2 x 4.5
C8 77 x 81 77 x 8.1 2.2 x 3.2
C9 40 x 57 40 x 5.7 1.6 x 2.2
C10 28 x 40 28 x 4.0 1.1 x 1.6
DL 110 x 220 11 x 22 4.33 x 8.66

Commonly used envelope sizes


We’ve highlighted some of the most commonly used envelope sizes below along with paper size they will hold. But with ‘c’ envelopes ranging from a large C0 to a tiny C10, there really is an envelope available for every job.

Pssst! Speak to us if you need any help with choosing an envelope, or any other aspect of your mail campaign for that matter. We’d love to help!

C4 Envelope Size


A standard C4 envelope is designed to fit unfolded A4 paper. It’s a good option for those important A4 documents you’d prefer not to have folded.

C4 Envelope Size

C5 Envelope size


A C5 envelope will accommodate A5 paper unfolded or A4 paper folded in half, a common size for brochures or flyers.

C5 Envelope Size

DL Envelope size


Known as the ‘letter envelope’ a DL is the perfect size for an A4 sheet of paper folded into 3. It’s also ideal for compliment slips which typically measure at 210 x 99 mm.

DL Envelope Size

If you found this article useful, we think you’ll like our guide to paper sizes and their many uses. 

Helping you choose the envelope for the job and much more


We’re a professional mailing house and print services provider based in Leeds, West Yorkshire. We have the know-how, equipment and resources to deliver on any direct mail campaign and do just that for a number of clients, big and small.

But it’s not just mail marketing we can help you with. We offer fully integrated print and mailing solutions so we can handle every aspect for you.

If you’re franking your mail you’re paying too much for your postage. We offer bulk postage rates guaranteed to be cheaper than franking or stamps.

Contact us today to see how we can help.