Collection: Large Letter Postal Boxes

Large letter postal boxes (also called PIP boxes — Pricing in Proportion) are flat-pack cardboard boxes designed to comply with Royal Mail's Large Letter dimensions: maximum 353 x 250mm and 25mm depth. Dispatching within this format saves significant postage compared to small parcel rates — the single most cost-effective change most small e-commerce businesses can make to their dispatch costs.

The range covers over 175 products across over 305 sizes, mapping to standard postal formats. Available in brown, white and black. Fully recyclable corrugated board construction.

Royal Mail Large Letter — Size and Weight Limits

• Maximum dimensions — 353 x 250mm, maximum 25mm depth.
• Maximum weight — 750g (including packaging).
• Minimum dimensions — 100 x 70mm, minimum 1mm depth.
• Key saving — Large Letter postage costs significantly less than Small Parcel for the same item.

Benefits of Large Letter Postal Boxes

• Royal Mail PIP compliant — designed to meet Large Letter maximum dimensions (353 x 250 x 25mm).
• Cost saving — Large Letter postage is substantially cheaper than Small Parcel for eligible items.
• Flat-pack storage — assembles in seconds; stores flat when not in use.
• Rigid card construction — protects contents from bending and light crush throughout transit.
• Recyclable — corrugated board, fully recyclable via kerbside paper and card collection.
• over 305 sizes — to match different product dimensions within the Large Letter format.

Frequently Asked Questions

What is the maximum size for a Royal Mail Large Letter postal box?
Royal Mail Large Letter maximum dimensions are 353 x 250mm, with a maximum depth of 25mm. The maximum weight is 750g including the box and all contents. These dimensions refer to the external packed measurements — the box itself takes up some of that depth, so the usable internal space is typically 18–22mm deep depending on the box construction.

How much can I save by using a Large Letter postal box?
The saving depends on the weight tier, but Large Letter postage is typically 30–50% cheaper than Small Parcel for the same item weight. For e-commerce businesses dispatching hundreds or thousands of items per month, switching eligible items from Small Parcel to Large Letter format can represent a significant reduction in annual postage costs. Use Royal Mail's online postage calculator to compare current rates for your specific weight.

Can I use large letter postal boxes with couriers other than Royal Mail?
Yes — large letter postal boxes are standard corrugated card boxes that can be dispatched with any courier. However, the 'Large Letter' designation and associated cost saving is specific to Royal Mail. Other couriers (DPD, DHL, Evri, Hermes) have their own size and weight categories — check the courier's current size guide to confirm whether a large letter format qualifies for their equivalent low-cost tier.

Are large letter postal boxes recyclable?
Yes — corrugated cardboard postal boxes are fully recyclable through standard kerbside paper and card collection. Remove any tape before recycling. The boxes are plain board with no coatings or plastic components that would affect recyclability.