Royal Mail Parcel Boxes

If you’re sending parcels with Royal Mail, getting your box size right isn’t optional. It’s the difference between cost-effective shipping and quietly overpaying on every single order. Our Royal Mail parcel boxes are sized to align with official guidelines, helping your shipments stay within the correct pricing bands while arriving safely and looking professional.

What are Royal Mail parcel size requirements?

Royal Mail sets strict size and weight limits for its most commonly used parcel categories.

For UK businesses, the key ones are:

Small Parcel: maximum 45 x 35 x 16 cm, up to 2 kg

Medium Parcel: maximum 61 x 46 x 46 cm, up to 20 kg

Even a slight increase in dimensions can push your parcel into a higher pricing tier. That means higher costs for the same product, simply because of the box you chose.

Using correctly sized Royal Mail parcel boxes helps avoid unnecessary surcharges, delays, or reclassification at the depot.

Our range of Royal Mail parcel boxes

We stock a wide range of Royal Mail compliant cardboard boxes across small and medium parcel categories, available in both new and used options. Whether you’re sending individual eCommerce orders or bulk shipments, our range is designed to help you stay within size limits without compromising on protection.

Our used boxes are particularly popular with high-volume shippers looking to reduce packaging costs while maintaining quality. Every box is checked before resale, so you can use them with confidence.

Small parcel vs medium parcel – what’s the difference?

Small parcel boxes are designed to maximise space while staying within tighter Royal Mail limits. They’re ideal for clothing, books, cosmetics and smaller consumer goods

Medium parcel boxes give you more flexibility for larger items, multi-item orders and bulkier or less uniform products.

Choosing between the two comes down to how efficiently you can pack your products without exceeding size thresholds.

Single wall and double wall – what’s the difference?

Single wall cardboard is lightweight and cost-effective, making it ideal for smaller, lighter products that don’t require heavy-duty protection.

Double wall cardboard includes an additional layer of fluting, making it stronger and more durable. It’s better suited for heavier items, fragile goods and shipments that may be stacked or handled more frequently.

If you’re shipping multiple items in one box or anything with a bit of weight behind it, double wall is often the safer choice.

New or used – both work for Royal Mail

Royal Mail does not require parcels to be sent in new boxes.

Used boxes are perfectly acceptable, provided they are structurally sound and free from damage. Our used Royal Mail parcel boxes are sourced, inspected, and ready to go. A practical way to reduce costs while keeping perfectly usable cardboard in circulation.

Why Reuseabox?

We’re a B Corp certified business supplying quality new and used cardboard boxes across the UK, with fast delivery and a range designed around real-world shipping needs. Whether you’re sending a handful of parcels a week or thousands a day, our Royal Mail parcel boxes help you stay compliant, reduce costs, and ship more efficiently.

Browse the full range to find the right size for your products, or get in touch if you need help choosing.