Cardboard Envelopes

Corrugated cardboard envelopes for UK online sellers — rigid all-board mailers that protect on both faces, not just one. Also sold as corrugated envelopes, rigid cardboard envelopes, cardboard envelope packaging or all-board mailers. Supplied flat in trade packs with peel-and-seal closure.

All-board, and why that's a different product from a board backed envelope

This is the distinction that decides which one you need, and it's worth two minutes.

A board backed envelope is a paper envelope with a stiff board laminated to one face. Thin, light, cheap to post, and ideal for photographs, certificates and prints — anything flat that must not bend.

A corrugated cardboard envelope is made of board throughout. Both faces are rigid, and the fluting between the liners gives it something a single board panel can't: cushioning. It resists crushing and impact as well as bending.

So the rule is about what you're sending, not how big it is. Flat paper items go in a board backed envelope. Items with any thickness, weight or fragility — small electronics, cosmetics, boxed jewellery, hard-backed notebooks, sample packs — go in a corrugated envelope. Sending a rigid item in a board backed envelope protects one side of it and leaves the other exposed.

What corrugated buys you over a padded bag

A padded mailer cushions but doesn't hold shape. Under compression in a full sack it deforms, and the contents deform with it.

Corrugated holds its shape. The flute is a structural arch, and it's the reason a thin sheet of corrugated resists a load that would crush the same weight of flat board. In practice that means the difference between an item that arrives as sent and one that arrives with a dented corner.

It's also cleaner to recycle. Paper padded mailers vary in what's inside them; this is one material throughout, and it goes in the paper collection whole.

Sizing, and the A4 question

Sizes run from small mailer formats up to large flat sizes, and the dimensions are in the table below rather than in this text, because the range moves.

A4 flat is the size most people are looking for. A4 is 210 × 297mm, so you need an envelope with clearance on both dimensions — sized exactly to A4 and the sheet won't go in square. Check the table and take the size above your item, not the one that matches it.

Measure the thickest point, not the flattest. A corrugated envelope has a fixed depth; unlike a gusseted mailer it doesn't expand. If your item is 20mm at the clasp or the spine, that's the number that matters.

Postage: most of these are Large Letter, one of them isn't

Royal Mail's Large Letter band allows 353 × 250mm and 25mm deep, up to 750g. Most sizes in this range sit inside that on their outer dimensions, and post at letter rates.

Two things to watch.

The largest size in the range exceeds Large Letter on length and will always be priced as a parcel. That isn't a fault — it's what the size is for — but don't standardise on it expecting letter rates.

And the size just below it sits close to the 353mm limit with very little margin. If you're relying on that band, measure a made-up sample rather than trusting the nominal dimension, because a packed envelope is fractionally larger than a flat one.

Depth is the one people get caught by. Corrugated is thicker than paper before you put anything in it. Weigh and gauge a packed sample before you commit a season's postage budget to a band.

Printed and bespoke

A corrugated envelope has a large, flat, unbroken face — one of the better print surfaces in postal packaging, and on most parcels it goes out blank.

Printed mailers get recognised in a stack of post, and for a seller whose product arrives by courier the outer is the first thing the customer handles. We quote on printed and bespoke sizes as part of a manufacturing group. Tell us the size, the run and the finish.

Buying by the pack

Supplied flat in trade packs, with price breaks as quantities increase. Flat-packed matters here: these arrive as sheets and take a fraction of the shelf space a made-up equivalent would.

Most sellers need two sizes — one that covers their standard product and one for the occasional larger order. Concentrating volume on two lines gets you further up the price break than spreading it across five.

We buy these as part of a manufacturing group, at volumes a reseller can't reach, and hold them across over 100,000 square feet of warehousing.

Delivery and returns

Next-day dispatch on UK mainland orders, with free UK mainland delivery and a £75 minimum order. Full terms on our delivery and returns pages.