For something that is so simple there is a lot of choice when it comes to selecting your envelopes. As well as choosing the size you also need to decide if you would like a window to display the recipient’s address, the method of closing the envelope and whether they need to be padded or protective in any way. To help with all these decisions we’ve created a handy guide to envelopes to help you select the most suitable products for your requirements.

If you’d prefer to talk to us or are buying in bulk then please call the Office Allsorts team on 0115 9455833.

Buyers Guide

Our envelope section covers a broad range of styles, sizes and types. To browse the category simply click on one of the product images above or for more information about the types of envelopes available please take a look at the buyers guide below.

Envelopes are available in a wide range of sizes and they have their own code structure in a similar way to paper. The table below shows the main envelope sizes available along with their measurements and the sizes of paper that will fit into them.

Envelope Size Guide

The international standard ISO 269 defines several standard envelope sizes which are designed for use with ISO 216 standard paper sizes.

Envelope FormatDimensions (MM)Dimensions (Inches)Recomended Use
C0 917 x 1297 36 1/8 x 51 1/16 Suitable for flat A0 size paper
C1 648 x 917 25 1/2 x 36 1/8 Suitable for flat A1 size paper or A0 size paper folded in half
C2 458 x 648 18 x 25 1/2 Suitable for flat A2 size paper or A1 size paper folded in half
C3 324 x 458 12 3/4 x 18 Suitable for flat A3 size paper or A2 size paper folded in half
C4 229 x 324 9 x 12 3/4 Suitable for flat A4 size paper or A3 size paper folded in half
C5 162 x 229 6 3/8 x 9 Suitable for flat A5 size paper or A4 size paper folded in half
C6 114 x 162 4 1/2 x 6 3/8 Suitable for A6 size paper or A4 size paper folded in half twice
C7/6 81 x 162 3 3/16 x 6 3/8 Suitable for one third A5 size paper
C7 81 x 114 3 3/16 x 4 1/2 Suitable for A7 size paper
DL 110 x 220 4 5/16 x 8 11/16 Suitable for one third A4 size paper

What types of envelope are available........

C4 Size Envelopes - Sometimes called A4 envelopes as you can fit a piece of unfolded A4 paper into them. C4 Envelopes are one of the most common sizes and are used for sending items such as reports or brochures. They are most commonly available in white or manila and also with a choice of a window or no window. Recently more colourful envelopes have become popular as they catch the eye more and so are ideal for marketing purposes or can be used to match a company branding. Once you’ve decided on colour then the type of seal must also be considered. Gummed envelopes, also called press seal, simply have glue on both the flap and the envelope body and these are pressed together to close the envelope. Peal and Seal envelopes have single adhesive strip on the flap. When you are ready to close the envelopes the protective cover is removed and the flap pressed onto the envelope body. Generally peal and seal are more expensive than press seal, however the gum or glue on press seal does degrade overtime and if not used within a few months won’t stick together very well. If you use your envelopes quickly then pres seal are recommended, if they are likely to sit in a stationery cupboard for some time then peel and seal would be the best option.

C5 Size Envelopes - Suitable for an A4 for sheet of paper folded in half or an unfolded piece of A5 paper. C5 Envelopes are commonly used for mail shots or business letter. The same colour options and means of securely closing C5 envelopes are available as they are with C4 envelopes. They are available in pack sizes starting from 25 up to 1000 per box.

C6 Size Envelopes - This size envelope is not generally used by businesses and is instead popular for sending greeting cards or post cards. One benefit that C6 envelopes do have is that they fall into the Royal Mail standard envelope size bracket and therefore attract a lower postage cost.

DL Size Envelopes - Are suitable for an A4 piece of paper folded twice so the finished sheet is a third of the unfolded size. A very common business size envelope used for sending letters and invoices. Also available in white or manila and with or without a window. DL envelopes differ from their larger counterparts as the flap or opening can commonly be found on either the long end or the short end.

Protective Envelopes - If the items you are posting are important and require some form of protection as they pass through the postal system then you have some excellent options. To prevent bending of documents board backed envelopes are available. The type of envelope comprises of a piece of rigid board and strong manila paper. Often they are printed with ‘Do Not Bend’ to ensure those handling the goods are careful of important contents. If you need to ensure your items stay dry then water proof polythene bags or mailing envelopes can be used. Both are burst and tear resistant and mailing bag are also tamperproof which adds an important level of security.

Gusset Envelopes - If you need to send over sized items such as books, magazines or manuals then gusset envelopes provide an ideal solution. Available with either a ‘Block Bottom’ or V-Shaped Bottom’ which allow the envelope to expand to accommodate larger items.

Padded Envelopes - Padded bags are commonly known as bubble bags and Jiffy bags and provide protection for delicate or bulky items which are to be sent through the post. They are generally made with a tear resistant outer layer that surrounds a bubble lined interior.

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