Envelopes

Rule of thumb: ruined by a crease, choose board backed. Ruined by a knock, choose corrugated. Too thick to lie flat, choose a book mailer.

Source: Royal Mail size and weight guide. Envelope sizes are flat dimensions. A gusseted envelope can expand past 25mm when packed, so measure it packed, not flat. The weight limit includes the contents.

Three products on this page, and they solve three different problems. Pick the wrong one and you either pay for protection you didn't need, or you get a bent print and a refund request.

The question isn't which envelope is best. It's whether your item needs rigidity, cushioning, or capacity — because no envelope gives you all three, and the one that tries costs more than it should.

Everything here is supplied in trade packs for UK sellers, with a £75 minimum order. Prices are shown per pack and exclude VAT.

Rigidity, cushioning or capacity

Pack quantities and current trade prices are on each product page.

A useful rule: if the item would be ruined by a crease, you need board backed. If it would be ruined by a knock, you need corrugated. If it's simply too thick to lie flat, you need a book mailer. 

Board backed envelopes are what photographers, print sellers and framing shops use to post work flat — a print that arrives creased is a refund and a bad review, and the board is what stops the crease happening.

The mistake that costs most is using a padded bubble envelope for a print. Padding absorbs impact — it does nothing at all to stop the whole envelope being folded through a letterbox.

Matching envelope size to paper size

Board backed envelopes follow the C-series, sized to take the matching A-series sheet without folding.

White stock costs slightly more and is worth it where the envelope is part of the presentation — greeting card brands, print sellers. For trade dispatch, brown does the same job for less.

Every board backed envelope carries a printed red "Please Do Not Bend" warning on the front. That isn't decoration — it changes how the item is handled at the sorting stage, which is the whole point of buying rigid.

Postage: where the sizes come from

Royal Mail's Large Letter band allows up to 353 × 250 × 25mm and 750g. Nearly every size on this page is built to sit inside it, because the step up to Small Parcel is a price jump, not an increment.

Two consequences worth knowing:

The C4 board backed envelope at 324 × 229mm is deliberately under the 353 × 250mm limit. It takes a flat A4 sheet and still qualifies as a Large Letter. That few millimetres of headroom is the entire reason the size exists.

The C3 at 457 × 324mm cannot be a Large Letter. It's too big in both dimensions, so it will always be charged as a parcel. Buy it because your A3 print needs to arrive flat, not because you expect to save postage — and if you're regularly sending A3, price a long postal tube against it, since rolling is cheaper if the artwork tolerates it.

The full band breakdown, including the 25mm depth trap, is on our postal boxes and mailers page.

Capacity: the gusset question

Book mailers and the larger cardboard envelopes have gussets — expandable sides that let the envelope grow to the depth of the contents rather than holding a fixed shape.

For a bookseller carrying stock in dozens of thicknesses, one gusseted size covers a range that would otherwise need three fixed formats — less inventory, fewer part-used packs, simpler picking.

The trade-off is that a gusset can expand past 25mm without you noticing, which quietly moves the item into Small Parcel. If you're packing to a band, measure the envelope packed, not flat.

Three things that catch people out

Buying board backed for books. Board backed stops bending, but it has no depth and no cushioning. A paperback in a C5 board backed envelope arrives with scuffed corners. Use a book mailer or a corrugated envelope.

Assuming "rigid" means "protected". Rigid resists bending. It doesn't resist crushing or impact. Anything semi-fragile wants the corrugated fluting.

Under-ordering the size you use most. Envelopes are supplied in packs of 50 and 125 depending on format. Concentrating volume into your two highest-use sizes almost always beats spreading across five — the break price improves and the picking bench gets simpler.

Not sure which formats fit your product mix? Send us your dimensions and typical weights and we'll work through it with you.

Printed and bespoke envelopes

A plain kraft envelope does the job. A printed one does the job and tells the recipient who sent it before they've opened anything.

For sellers shipping regularly, print earns its cost in two ways: it makes the parcel recognisable in a stack of post, and it turns the outer packaging into the first thing the customer sees rather than the thing they throw away. For photographers and print sellers in particular, an unbranded envelope undersells what's inside it.

We handle bespoke work as part of a manufacturing group, so print, sizing and specification are all things we can quote on rather than things you have to take as they come. If the size or finish you need isn't on this page, ask — tell us what you're sending and how you want it to arrive and we'll come back with options.

Free delivery to the UK mainland on every order, with a £75 minimum. Buying as part of a manufacturing group means we source these at volumes a reseller can't reach, and that's what keeps the trade price where it is.

Still deciding?

• Sending books, records or media? Variable-depth book wraps and record mailers fold to the contents and often beat an envelope on cost.
• Item won't lie flat? See postal boxes and mailers — sized to the Royal Mail bands.
• Need protection more than a flat profile? See cardboard boxes for single and double wall.
• Something light and non-rigid? See padded and paper mailing bags.