royal mail postage boxes

Sellers choose royal mail postage boxes that are made to sit inside a specific Royal Mail size and weight band, so the postage they pay matches the product they send. Using royal mail postage boxes with accurate external dimensions removes guesswork at the packing bench, protects contents better than envelopes and helps slim orders pass through the letterbox.

The Royal Mail bands behind royal mail postage boxes

Royal Mail prices by format as well as weight. A letter measures up to 24cm by 16.5cm and 0.5cm thick at up to 100g. A large letter measures up to 35.3cm by 25cm and 2.5cm thick at up to 750g for most services. A small parcel measures up to 45cm by 35cm by 16cm at up to 2kg, and a medium parcel measures up to 61cm by 46cm by 46cm at up to 20kg. Always check the current figures on the Royal Mail size and weight guidance before you settle a box size, because limits and service rules can change.

The measurement that counts is the finished packed item, including the box walls, contents, inserts and any outer wrap. A box bought to a nominal size can still tip into the next band if it is overfilled and bulges, so pack consistently and weigh a finished sample order. Our postal boxes by size category groups formats by the job they do, from letterbox slim packs to small parcel cartons.

Large letter boxes for slim orders

Large letter boxes suit flat goods such as documents, prints, cards, slim books, phone cases and compact accessories. Their rigid walls stop bending in sorting and transit, and their shallow depth is made for letterbox delivery, which cuts missed deliveries. Browse large letter postal boxes and letterbox postal boxes for the core formats, with A5 postal boxes for half A4 contents and C4 postal boxes for A4 sheets that must stay flat.

Small parcel boxes for deeper orders

When a product is deeper than 2.5cm or heavier than 750g, design for the small parcel band from the start instead of forcing a large letter fit. A small parcel box gives room for protective padding around fragile items and for multi item orders. The small postage boxes range covers this everyday ecommerce territory, and a close fit still matters, because empty space invites movement and damage.

Board, protection and print

Most Royal Mail sized boxes use single wall corrugated board, which balances low weight with useful crush resistance. Weight matters twice here, once for the band limit and once for your postage cost on every order, so avoid over specifying board for light goods. For fragile contents, add a fitted insert, tissue or a card stiffener rather than a thicker box wall, and keep the total packed depth inside your band.

Adding your branding without risking the band

Print your logo and a short message on the lid and sides so the parcel is recognisable on arrival. Keep the address and label zone clear, and remember that tape and labels add almost nothing to size, while bulky outer sleeves or extra wrap can add depth. Custom Postal Boxes prints in house in Wolverhampton, with free design support, low minimum order quantities and free UK delivery, and plain or printed runs are both quoted by size, material and quantity with no fixed prices listed.

Choosing and checking your box size

List your typical orders by product size and weight, pick the band each one should travel in, then choose the smallest box that holds the product, its protection and a small packing allowance. Test a packed sample against the band limits with a tape measure and scales before a full run, and repeat the check when your product or insert changes. To order, contact the team for a quote with your target band and internal size.

FAQs about Royal Mail sized packaging

What sizes does Royal Mail use for letters and parcels?

A letter is up to 24cm by 16.5cm by 0.5cm and 100g, a large letter is up to 35.3cm by 25cm by 2.5cm and 750g, a small parcel is up to 45cm by 35cm by 16cm and 2kg, and a medium parcel is up to 61cm by 46cm by 46cm and 20kg.

Why does my box need to be measured when packed?

Royal Mail measures the finished item you hand over, including box walls, contents and wrap. A box that bulges when overfilled can move into a higher band, so weigh and measure a real packed sample before ordering in volume.

Can Royal Mail sized boxes carry my branding?

Yes. Your logo, colours and messages can be printed on the lid and sides, with the label area kept clear. Free design support will position artwork for the box size and band you choose.

What if my product does not fit the large letter band?

Choose a small parcel box instead and design for that band from the start. The extra depth gives room for padding and multi item orders, and a close fit inside the band still keeps movement and damage down.