postage box

A postage box is a cardboard box sized and built for sending goods through the post or by courier, protecting the contents while keeping the parcel within an economical size and weight band. Choosing the right postage box matters because Royal Mail and other carriers price by size as well as weight, so a box that fits your product closely protects it better and can cost less to send.

How to choose the right postage box size

Start with the product, not the box. Measure the item at its widest points, add its packaging such as sleeves, pouches or inner cartons, and then choose internal box measurements slightly larger than that total. A small margin lets you add a layer of tissue or paper cushioning without forcing the lid. Too much spare space lets the product slide and break, and pushes the parcel into a larger size band. Our postal boxes by size groups the main formats so you can compare them quickly.

Royal Mail size bands a postage box must respect

Royal Mail large letters can measure up to 353 mm by 250 mm by 25 mm and weigh up to 750 g. Small parcels can measure up to 450 mm by 350 mm by 160 mm and weigh up to 2 kg, and medium parcels up to 610 mm by 460 mm by 460 mm and 20 kg. The Royal Mail small parcel guidance confirms these limits. Slim products belong in a shallow letterbox postal boxes style box, typical online orders suit small postage boxes, and only genuinely bulky goods need a medium parcel format.

Internal and external measurements explained

Carriers judge the external size of the finished parcel, including tape and any bulge, while you pack into the internal space. Board thickness sits between the two figures, so a box advertised by its external size holds less than it appears to. Measure your packed product, match it to the internal size, and then check the external size against the band you intend to use before you commit to a quantity.

Materials and styles of postage box

Most designs use corrugated cardboard because it is light, strong for its weight and widely recyclable, and our cardboard postal boxes cover the main constructions. Single wall board suits light and everyday goods, while double wall board suits heavy or fragile contents. Folding mailer styles with hinged lids pack quickly and present well, and printed versions carry your logo and colours so a plain delivery becomes a branded one. Kraft finishes give a natural look, and white board gives a clean surface for detailed print.

Buying a postage box from Custom Postal Boxes

Custom Postal Boxes manufactures postal and mailer boxes in house in Wolverhampton and offers custom sizes, custom printing, low minimum order quantities, free design support and free UK delivery. That combination suits independent shops that need a modest first run and larger sellers that reorder regularly. Pricing depends on size, material and quantity because the business works on quotations rather than fixed list prices. Send your product dimensions and the quantity you need through our contact page and a specification and quote will be prepared for you.

FAQs about a postage box

What is a postage box?

A postage box is a cardboard box designed for sending products through the post or by courier. It protects the contents in transit and is sized to fit carrier size bands, so the parcel travels at the correct rate without wasted space or unnecessary cost.

How do I measure for a postage box?

Measure your product at its widest points, including any inner packaging, then choose internal box dimensions slightly larger so cushioning fits without forcing the lid. Finally check the external dimensions of the sealed parcel against the carrier size band you plan to use.

What is the difference between a postage box and a shipping box?

The terms overlap and both describe cardboard boxes for sending goods. Postage box usually refers to smaller boxes for individual postal orders, while shipping box often means larger or stronger cartons for heavier goods, trade deliveries or several items packed together.

Can a postage box be printed with my branding?

Yes. A postage box can be printed with your logo, colours, artwork and messages on the outside, and often inside the lid as well. Printed postal packaging helps customers recognise your brand on arrival and makes a standard delivery feel more professional.