a3 postage box

An a3 postage box is a flat sturdy postal box sized to hold A3 paper which measures 297 mm by 420 mm plus a small margin for safe handling. Custom Postal Boxes makes each a3 postage box to order in Wolverhampton so prints artwork and documents travel flat without folded corners or bent edges.

Choosing an a3 postage box that keeps work flat

The main job of an a3 postage box is to stop large sheets flexing in transit. A snug internal fit matters more than extra space because loose prints slide and their corners strike the box walls. Measure the largest sheet or mounted print you send then allow a few millimetres of clearance on each side for a protective sleeve or tissue wrap. If you post framed or mounted work the depth must cover the frame thickness plus padding on both faces.

Board grades for large flat items

Corrugated cardboard is the usual choice for this format because the fluted layer resists bending across a wide span. A single wall board suits paper prints and card artwork while a stronger grade helps with mounted boards calendars and heavier portfolios. Kraft board gives a natural finish and white board gives a cleaner surface for full colour print.

Why stiffness matters at A3 size

A wide flat panel can bow in the middle when a parcel is carried by one edge. Stiffer board spreads that load across the whole panel so the contents stay flat. Creased corners and firm folds also add strength without adding much weight.

How an a3 postage box is classed by Royal Mail

A3 sheets are longer than the Royal Mail large letter limit of 353 mm so a packed a3 postage box normally travels as a small parcel provided it stays within 450 mm by 350 mm by 160 mm and under 2 kg. Deeper boxes for framed work may move into the medium parcel band so always measure the finished parcel rather than the sheet inside. Check the current bands on the Royal Mail prices page before you buy postage.

Ways to protect prints inside the box

Place prints in a clear sleeve or wrap them in tissue then tape the bundle lightly to a stiff card sheet so it cannot drift. Add a second card sheet on top for crush protection and fill any depth gap with crumpled paper so nothing rattles. Write the delivery address clearly and mark the parcel as flat artwork where that helps careful handling. Our Cardboard Postal Boxes and the Postal Boxes by Size range show the formats most print sellers start from.

Print and ordering options for an a3 postage box

Printing your studio name or shop logo on the lid turns a plain transit box into a recognisable delivery. Many sellers add care wording inside the lid that tells buyers how to open the box without cutting into the print beneath. Sizes can follow our Small Postage Boxes construction or a fully bespoke footprint and our Printed Postal Boxes show print coverage options. Ordering is quote based and the price depends on size material and quantity with low minimum order quantities free design support and free UK delivery. Send your sheet size and typical order weight through our contact page for a quote and we will size the box around your work.

FAQs about a3 postage box sizes and posting

What size is an a3 postage box?

An a3 postage box is sized around A3 paper at 297 mm by 420 mm with a few millimetres of clearance so sheets slide in without catching. Depth varies with what you send from slim boxes for loose prints to deeper boxes for mounted or framed work.

Is an a3 postage box a large letter or a parcel?

A packed a3 postage box is normally a small parcel because A3 length passes the large letter limit. It stays in that band while the parcel measures no more than 450 mm by 350 mm by 160 mm and weighs under 2 kg.

How do I stop A3 prints bending in the post?

Sandwich the prints between two stiff card sheets inside a rigid corrugated box and fill any spare depth so the bundle cannot move. A snug box stops corner impacts which are the most common cause of bent edges.

Can an a3 postage box be printed with my logo?

Yes. The lid and outer panels can carry your logo artwork and handling wording and the inside lid can hold opening guidance or a thank you message. Free design support is included before you approve the final layout.