A Size Guide for Our Card, Envelope and Paper Supplies

Posted by Beth on 26th Jan 2021

A Size Guide for Our Card, Envelope and Paper Supplies

The Paperbox is your one-stop online shop for all your card and paper supplies, from our popular A4 card and paper sheets to card blanks and envelopes — all sourced from our partner paper mills and merchants in the UK and Europe.

When choosing paper and card supplies for your DIY cards or event invitations, we know it can be difficult to decide what size of paper to get. With so many size options available, we thought we’d make things easier for you with this paper, card and envelope size guide.

Paper and Card Sheets

The Paperbox offers premium paper and card sheets in the following sizes.

Our paper and card sizes are organised using the ISO 216 standard, which includes the common A4 size used in most countries except Canada, the United States, Mexico, Colombia and the Dominican Republic.

The “A” system is organised through an ascending sequential order. In other words, the lower the number after the “A”, the larger the paper size. For example, A4 is double the size of A5, A5 is double the size of A6 and so on.

Below are two diagrams showing our paper and card sizes, giving you a visual representation of how A5, A6 and A7 paper sizes fit inside an A4 sheet of paper.

We also have a collection of 5” x 7” paper and cardstock in different colours and finishes, perfect for elegant crafting and card making.

Card Blanks

The Paperbox offers pre-creased card blanks in the following sizes.

Our card blanks are described by their measurements once folded — that is, the front-facing side of the card. For example, an A5 card blank is an A4 sheet — which, when folded in half, becomes a card with an A5-sized front.

We also offer card blanks in small square and large square sizes. These are perfect as speciality greeting cards for birthdays, thank you cards and corporate celebration cards.

Below is an image that breaks down the card blanks we provide and their size in relation to an A4 size sheet of paper.

Be sure to check out our collection of pre-creased and flat packed 5” x 7” card blanks, available in a wide variety of colours and elegant finishes.


Our premium envelopes are available in C5, C6, C7, large square, small square and 5” x 7” sizes.

Unlike paper sheets and card blanks, envelope sizes are categorised using a “C” and an accompanying number — the latter corresponds to a matching paper or card blank size. For example, a C5 envelope will fit an A5 card blank or an unfolded A5 sheet of paper.

We also carry a collection of 5” x 7” envelopes for your event invites, wedding invitations and greeting cards.

Note that each envelope’s measurements are slightly larger than the actual size of the card blank or sheet, providing enough room for anything else that may need to be added. If they were the same size as the card, the card would never fit inside. This is particularly important for 5” x 7” envelopes, which, despite their name, are actually slightly larger (measuring 5.2” x 7.2”) than 5” x 7” inserts.

Here’s a visual breakdown of the envelopes and their matching card blanks available on The Paperbox, with their sizes illustrated in relation to an A4 size sheet of paper.

If you need a quick visual reference guide while shopping for our card and paper supplies, go ahead and save the image below.

Quick Reminders before Choosing Paper Sizes

Although the “A” paper size system is used around the world, it may not be familiar to consumers in North America as well as parts of South America and Asia that use inch-based systems. Examples of loose paper sizes under this system include Letter, Legal and Tabloid.

Furthermore, the “A” system should not be confused with the SRA paper size system. SRA, which stands for “supplementary raw format A,” is typically used for printing and is slightly larger than standard “A” series sizes.

Order Now to Get Free UK Shipping on Select Orders

Order your paper supplies, card blanks and envelopes from The Paperbox to get FREE standard UK shipping on select orders. We also offer express delivery and next-day delivery for urgent orders. The Paperbox also ships to the Republic of Ireland and select parts of Europe. Visit our Delivery and Returns page for more details.

Whatever the occasion, make it personal and special with premium-quality paper and card supplies from The Paperbox.