custom size mailer boxes

Custom size mailer boxes are mailer boxes manufactured to the dimensions of your product rather than picked from a stock list, so the contents sit snug with less filler and less wasted space. Custom Postal Boxes produces custom size mailer boxes in Wolverhampton, with low minimum order quantities, free design support and free UK delivery on every order.

Why custom size mailer boxes outperform stock sizes

A stock box is always a compromise, because your product was not designed around it. The gap is filled with void paper, air pillows or extra board, all of which add cost, weight and packing time to every single order. A box made to your size removes most of that waste and holds the product still, which is the main defence against damage in transit. Our custom mailer boxes UK range is built this way as standard, and regular sellers find the savings repeat across hundreds of parcels, not just the first order off the bench.

How to measure for a made to measure mailer

Measure the product as it will be packed, including tissue, a protective sleeve or any booklet that travels with it. Record length, width and height in millimetres, then add a small clearance of a few millimetres per side so staff can pack quickly without forcing the lid. If several products ship together, measure the combined bundle in its usual arrangement. Share the weight too, because a heavy bundle may need a stronger flute even when the dimensions stay the same.

Internal and external dimensions explained

Box makers quote internal dimensions, meaning the usable space inside the folded box. External dimensions are larger by roughly twice the board thickness, and carriers judge size bands on the external size. When you check a postage band, always test the packed external size, including any bulge at the lid, so a few millimetres of board do not push the parcel into a higher price band.

Board grades used in custom size mailer boxes

Most mailer boxes use corrugated cardboard with an E flute or B flute profile. E flute is thin and smooth, ideal for print and for lighter goods such as clothing, prints and cosmetics. B flute gives more cushioning and stacking strength for jars, bottles and electronics. Kraft board shows a natural brown finish, while white board gives brighter print. For fast packing, self seal mailer boxes close with a peel strip, and the cardboard mailer boxes range shows plainer styles where branding sits on a label or sleeve instead.

Keeping custom sizes inside postage bands

Royal Mail prices parcels by size band as well as weight, with small parcels limited to 450mm by 350mm by 160mm and 2kg, and medium parcels up to 610mm by 460mm by 460mm and 20kg. Designing your box a few millimetres inside a band boundary can save money on every parcel for years. Review the current Royal Mail price guidance when you fix a new size, and remember that tape, labels and slight bulging all count towards the size the carrier measures.

Ordering custom size mailer boxes step by step

Send your packed product dimensions and weight, tell us how the order is usually sent and share any artwork you have. Pricing depends on size, material and quantity, so the clearest brief gives the firmest quote. Low minimums mean you can prove a new size on live orders before rolling it out across the range, and repeat orders keep the same dimensions every time. Begin through our contact page for a quote and the team will confirm the best flute, closure and print layout for your product.

FAQs about custom size mailer boxes

What are custom size mailer boxes?

Custom size mailer boxes are manufactured to the exact internal dimensions your product needs. A close fit protects better than a stock box, reduces filler and packing time and can keep parcels inside a lower postage band.

How much clearance should I add when measuring?

Add a few millimetres on each side of the packed product so the item slides in easily and the lid closes without strain. Measure the product wrapped exactly as customers receive it, including tissue or booklets.

Can a custom size reduce my postage costs?

It can. Royal Mail charges by size band as well as weight, so a box designed to sit safely inside the small parcel limits can cost less to send than an oversized stock box carrying the same product.

What is the minimum order for custom size mailer boxes?

Low minimum order quantities apply, which suits testing a new size before a larger run. Pricing depends on size, material and quantity, and every order includes free design support and free UK delivery.