large letter boxes UK

large letter boxes UK are slim cardboard boxes that keep a packed parcel within Royal Mail large letter limits of 353mm by 250mm by 25mm and 750g. Staying inside those limits lets large letter boxes UK travel at large letter rates and pass through most letterboxes, so the customer does not need to be at home. Custom Postal Boxes makes them in Wolverhampton with custom print and free UK delivery.

The Royal Mail limits behind large letter boxes UK

Size and weight both matter, and either one can reclassify your parcel. Length must not pass 353mm, width must not pass 250mm, depth must not pass 25mm and the finished parcel must weigh no more than 750g on standard large letter services. The box, the product, any wrap, the label and the tape all count. A box described as large letter size can still fail if it is overfilled and the lid rises, so judge the packed parcel, never the empty box.

Contents that fit the format well

A4 documents, certificates, magazines, paperback books, greetings cards, slim clothing, phone cases, cosmetics compacts, jewellery in slim boxes and craft supplies all suit this format. Group contents flat rather than stacked in a lump, spread weight evenly and keep rigid items away from the edges where letterbox slots and sorting equipment apply pressure.

The letterbox test at the delivery address

Royal Mail limits and a real letterbox are two related but separate tests. Most standard letterboxes accept large letter sized parcels, yet older or narrow slots can be tighter. Slim flexible contents travel best, and clear addressing with a safe place instruction helps where a slot proves too small. When in doubt for a bulky order, a small parcel box is the honest choice.

Choosing and packing large letter boxes UK

Pick a box with a little margin under each limit rather than one that touches all three, because board thickness, tape and contents vary slightly between packs. The Royal Mail size and weight guidance sets out the bands in full. Our large letter postal boxes are the core product, with letterbox postal boxes for orders where doorstep delivery matters most and C4 postal boxes for A4 contents close to the width limit.

Packing steps that keep you in band

Fold the box square, place contents flat, add only thin protection such as a board stiffener or paper wrap, close the lid without forcing it and lay tape flat along one seam. Weigh the finished parcel on a bench scale and measure depth at the thickest point, including the lid. Record the result for each product line so new staff pack to a known standard rather than guessing.

Print and ordering for UK sellers

Even a slim box has two large faces for branding. A logo and web address on the top face make the parcel recognisable in a hallway pile, and a short message inside the lid is read the moment it opens. Print in a strong colour that survives handling, keep small text off fold lines and check artwork with our free design support before production, especially where a design runs close to the edges of a shallow box.

Pricing depends on size, material and quantity and is supplied by quote. Minimum order quantities are low, boxes are manufactured in house in Wolverhampton and UK delivery is free. Send your product measurements and target quantity through our contact page for a large letter box quote and say whether the parcel must also pass a letterbox, because that detail shapes the depth we recommend.

When to step up to a small parcel box

Choose a small parcel box when contents pass 25mm deep once wrapped, when total weight passes 750g or when fragile goods need thicker protection than a slim box allows. Paying the correct rate for a well protected parcel is cheaper than refunds, resends and poor reviews from items crushed to fit a letter format.

FAQs about large letter boxes UK

What is the maximum size for a Royal Mail large letter?

The maximum is 353mm long, 250mm wide and 25mm deep, with a maximum weight of 750g for standard large letter services. The measurement covers the whole packed parcel, including the box, contents, wrap and tape.

Will a large letter box fit through every letterbox?

Most standard letterboxes accept parcels within large letter limits, but slot sizes vary, especially on older doors. Slim flat contents give the best chance, and very rigid or full boxes may still need the customer to be at home.

What products suit large letter boxes UK?

Flat and slim goods such as A4 documents, magazines, paperbacks, cards, slim clothing, phone cases and small boxed cosmetics suit this format well, provided the packed weight stays within 750g.

Can large letter boxes be printed with my logo?

Yes. The top and base faces take logos, colours and messages clearly. Custom Postal Boxes offers free design support, low minimum order quantities and free UK delivery.

What happens if my parcel is slightly too deep?

It will be classed as a small parcel and charged at that rate, and it may not fit through letterboxes. Leave a small margin under 25mm when packed and check depth at the thickest point before posting.

A large letter box rewards precision, and a few millimetres of care at the packing bench protect your postage rate on every order.