Envelope size guide
Buyers Guides

Envelope size guide

Ever tried to order an envelope but not quite sure what type you really need or whether your mail will fit? Whether you want to post a single letter or mail an item of clothing, our guide will help you decide which envelope you need.

We’ve broken down everything you need to know about envelope sizes and which ones you should always keep in stock.

Discover the right size for you:

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The C6 envelope is our smallest envelope on this list, making it ideal for mailing small trinkets, USB sticks or memory cards without having to send a parcel.

DL size envelopes are one of the most widely used options available. This envelope accommodates A4 paper folded into thirds lengthways and is usually recognised as the standard type used by businesses when mailing out one to three page letters. If you regularly send mail, we’d recommend stocking up on DL envelopes.

The same size as A5 paper, the C5 envelope is another popular choice as it’s made to fit an A4 piece of paper folded in half lengthways. This type of envelope is more suitable than the DL if you’re posting slightly longer letters, as folding sheets of paper into halves rather than thirds provides room for more pages. You could also use a C5 to hold a small journal, slightly larger greetings cards or even printed photos.

If you regularly send larger documents, a B4 envelope could be perfect for you. Big enough to accommodate A4 paper, it’s also available with added depth. This means you can mail thick documents, contracts or small boxes at a cheaper cost than a parcel.

A C4 envelope is designed to accommodate a full page of A4 paper. Great for small printed documents, certificates and magazines, this is a very common type of envelope. We’d recommend keeping a stock of these close to hand in the office, for documents that you can’t fold into a DL.

Made to fit A3 paper, a C3 envelope is the biggest envelope you’ll need before moving on to a parcel or postal tube. Usually used for posters that you don’t want to bend or flattened out clothing, we’d recommend purchasing this in a thicker paper or card to avoid damaging your mail.

Use our envelope size guide to discover the measurements you need to know and to identify the right envelope for your needs.