Paper envelopes: how to choose the right size, closure and quantity

An envelope may seem like nothing more than a simple stationery item. However, choosing the wrong size, paper that is too thin or an unsuitable closure can make your post difficult to insert, less presentable or more vulnerable during transit. Whether you are an individual or a business, it is therefore worth checking a few details when choosing your paper envelopes.

Before placing your order, three mistakes are particularly common:

• Relying solely on colour or design: an elegant white envelope or a kraft envelope with a natural look will not necessarily be suitable for its contents.
• Confusing sizes: an A4 sheet folded in half does not require the same envelope as a document sent flat.
• Overlooking the type of closure: a self-seal envelope makes it easier to prepare a batch of letters, while a gummed envelope is better suited to traditional correspondence.

What to check before buying paper envelopes

1. The size: C5, C6, DL or C4

The size mainly depends on how the document will be folded:

• DL envelopes – 110 × 220 mm: these generally hold an A4 sheet folded into three. They are suitable for administrative letters, invoices, business correspondence and everyday post.
• C6 envelopes – 114 × 162 mm: these are suitable for an A4 sheet folded into four, as well as cards, invitations, short notes and thank-you messages.
• C5 envelopes – 162 × 229 mm: these allow you to insert an A4 sheet folded in half. This size is practical for short files, official letters and documents that should remain relatively lightly folded.
• C4 envelopes – 229 × 324 mm: these are designed for sending an A4 sheet flat, without folding it. They are suitable for reports, posters, illustrations, files and administrative documents.

Always remember to check the internal dimensions, especially if your post contains several sheets or a thick card.

2. Paper and paper weight

Paper weight refers to the weight of the paper per square metre. At 90 g/m², an envelope generally offers a good balance of flexibility, structure and durability for everyday correspondence.

Kraft paper provides greater rigidity and a more natural appearance. For example, Clairefontaine Milleraies kraft envelopes use 90 g/m² virgin-fibre paper, with stated tear resistance and PEFC certification, according to the product details. For documents sent flat, the C4 size prevents creasing and makes insertion easier.

White envelopes are often preferred for formal correspondence. Some references offer a high level of whiteness and a grey-printed interior, which can make the contents less visually noticeable.

3. The type of closure

The best choice mainly depends on the volume of post you need to prepare and how often you use the envelopes:

• Self-seal envelopes: simply remove the silicone strip protecting the adhesive, then press down the flap. This solution avoids having to moisten the glue and is particularly practical for repeated postage.
• Gummed envelopes: the flap is sealed by moistening the adhesive area. They are often associated with invitations, handwritten letters and more traditional correspondence.
• Elastic or document-wallet closure: this type of storage does not always replace a postal envelope, but it may be better suited to organising and transporting several documents.

For professional use, also check the number of units per pack. A pack of 15 envelopes may be enough for an occasional need, while a pack of 25 will be more practical for a mailing campaign or sending invitations.

Our selection based on how you use them

Recommended for : Beginners and smaller budgets

CLAIREFONTAINE 9916C – 25 white C6 envelopes

Why this choice suits this profile : The C6 size is suitable for cards, invitations and short letters. The pack of 25 gives you a useful supply without buying too many.

How this product helps you avoid the pitfall

The dimensions are clearly stated, and the self-seal closure avoids mistakes caused by moistening the flap.

Main benefit and key features

90 g/m² paper, C6 size, 25 envelopes and FSC certification stated in the product details.

Recommended for : Lovers of beautiful stationery

CLAIREFONTAINE LALO – 25 gummed C6 envelopes

Why this choice suits this profile : The textured laid white paper is particularly well suited to invitations, menus, announcements and personalised messages.

How this product helps you avoid the pitfall

The laid texture is clearly mentioned in the product details, so it is not simply a visual effect without a precise description.

Main benefit and key features

C6 size, gummed flap, laid white paper and a surface stated as suitable for personalised printing.

Recommended for : Special occasions and regular postage

CLAIREFONTAINE 75015C – 15 kraft C4 envelopes

Why this choice suits this profile : The C4 size lets you send A4 documents flat, including reports, files, posters and illustrations.

How this product helps you avoid the pitfall

The size is designed for unfolded sheets, while the self-seal closure speeds up the preparation of multiple items of post.

Main benefit and key features

90 g/m² kraft paper, 15 units, stated virgin fibres and PEFC certification.

Recommended for : Celebrations and cash gifts

Glitter Chinese red hongbao envelopes – pack of 6

Why this choice suits this profile : These Chinese gift envelopes are suitable for celebrations, weddings, birthdays and other occasions when money is given as a gift.

How this product helps you avoid the pitfall

The product details specify a glittery red film with hot-stamped gold lettering, giving you a more accurate idea of the finished look.

Main benefit and key features

Pack of 6, embossed gold designs and a presentation suited to hongbao, the famous Chinese red envelopes.

Frequently asked questions about paper envelopes

What size should I choose for an A4 letter ?

For an A4 sheet folded into three, choose DL envelopes. For folding in half, C5 envelopes are more suitable. If you want to avoid creasing altogether, choose C4 envelopes.

Do self-seal envelopes keep for a long time ?

Store them in a dry place at a stable temperature, away from moisture. The silicone strip should remain intact until the envelopes are used. A damp environment may gradually affect the adhesive.

Are gummed envelopes suitable for invitations ?

Yes. They are often chosen for invitations, announcements and personalised correspondence. However, you will need to seal the flap by moistening it and store the envelopes flat to prevent them from becoming misshapen.