Opening The Flap on Envelopes: A Guide to the Popular Sizes


In the realm of business communication and beyond, envelopes play a crucial role in ensuring professionalism, security, and brand representation. Whether you’re sending out invoices, marketing materials, wedding invitations or personal correspondence, choosing the right envelope size is essential. At Dynamic Print, we understand the importance of envelope sizes for various purposes. In this short guide, we’ll explore the common envelope sizes used in the UK, catering to both business and personal needs.

Standard UK Envelope Sizes:

· DL

– 110mm x 220mm (4.33 inches x 8.66 inches)

– Commonly used for mailing documents, letters, invoices, and other business correspondence.

– Fits an A4 sheet folded into thirds or an A5 sheet folded in half.

· C3

– 324mm x 458mm (12.76 inches x 18.03 inches)

– Suited for large documents or posters, ensuring they remain flat and secure during transit.

· C4

– 229mm x 324mm (9.02 inches x 12.76 inches)

– Designed to accommodate unfolded A4 documents, brochures, and larger mailings.

· C5

– 162mm x 229mm (6.38 inches x 9.02 inches)

– Suitable for bi-folded A4-sized documents or A5 invitations.

· C6

– 114mm x 162mm (4.49 inches x 6.38 inches)

– Ideal for sending A6-sized cards, invitations, and smaller documents.

· C7

– 81mm x 114mm (3.19 inches x 4.49 inches)

– Often used for smaller items such as gift cards, RSVPs, or compact notes.

· C8

– 57mm x 81mm (2.24 inches x 3.19 inches)

– Suitable for very small items like tiny notes, gift tags, or small RSVP cards.

Specialty Envelope Sizes:

In addition to the standard sizes mentioned above, many more specialty envelope sizes and styles are available to meet diverse needs. From square envelopes to oversized envelopes, the options are vast. Whether you require small, elegant envelopes for wedding invitations or large, robust envelopes for mailing catalogues, there’s a size and style to suit every occasion. Specialty envelopes can also feature unique designs, colours, and textures, adding a touch of personality and flair to your correspondence. For a comprehensive selection of envelope sizes and customisation options, give us a call to discuss the best solution.

Sealing Options:

When it comes to sealing your envelopes, there are several options to consider. Traditional gummed envelopes require moisture to seal securely, while self-seal envelopes feature an adhesive strip that makes sealing quick and convenient. For added security, peel-and-seal envelopes offer an extra layer of protection, ensuring your contents remain confidential during transit. At Dynamic Print, we offer a variety of sealing options to suit your preferences and mailing needs, ensuring your correspondence reaches its destination safely and securely.


Selecting the right envelope size and sealing option is crucial for both business and personal communication needs. Understanding the various envelope sizes available in the UK market empowers you to make informed decisions that align with your requirements and budget. At Dynamic Print, we offer a wide range of envelope sizes, sealing options, and customisation choices. Let us help you make your correspondence, whether business-related or personal, effective, professional, and secure. Visit us at to explore our range of envelope solutions or call us on 01603 40040.

Envelopes Printing

Glossary of Envelope Terms

Why we think choosing the right envelope is sometimes more important than what is actually in it.

Envelopes as far as we are concerned are one of the most important part of your print project, Why? Because it is generally the first thing your customer will see when it arrives on their doorstep.

Extensive research over the years has shown that using a coloured or textured envelope, personalised, hot foiled or debossed envelope will get you and your company noticed,.

The research has shown that the end user will engage with the product inside the envelope much longer than if it had arrived in a standard white or brown envelope. Think about how you feel when you have had a hand written letter arrive or a bright coloured envelope sat on your mat waiting to greet you. We cannot wait to open it to see whats inside. Lets face it, better than finding a bill or hospital letter ????

Envelopes can come in so many different shapes, sizes & finishes that it can be rather confusing, to know which envelope is best suited to your project, for instance, if your brochure weighs over 200gsms we may want to consider a hard backed envelope ..

Some of the terminology is confusing for instance do you know the difference between a gusset or a banker? A peel & seal or a self seal?

Click here to read our Glossary of Envelope Terms

Final points to think about, by choosing the right envelope you will always make a good first impression and lets face it first impressions count more nowadays than ever.

Make the envelope look too important to just throw away and disgard

By choosing the right envelope it can say an awful lot about your company it can demonstrate your concerns for the environment to using coloured envelopes to play on human curiosity.

It is proven a distinctive envelope can increase your mailing success by up to 40%.

Statistics show that a stylish coloured envelope is 9 times more likely to be opened than a bland white or manilla one

70% of mail is generally opened up over the bin – make sure your leaflet is not one that is thrown before even opened.