What size box counts as a Royal Mail Large Letter?

A Royal Mail Large Letter must be no bigger than 353mm x 250mm x 25mm and weigh up to 750g. Every box in this range is 20mm deep, so it stays inside the 25mm depth limit and is charged at the Large Letter rate rather than as a Small Parcel.

What does PIP mean on postage boxes?

PIP stands for Pricing in Proportion, the Royal Mail system that prices post by size as well as weight. PIP compliant postage boxes are made to fit the Letter, Large Letter or Small Parcel dimensions so you always pay the lowest possible band for your item.

What is the difference between Large Letter and Small Parcel postal boxes?

Large Letter boxes are shallow — 25mm deep or less — and suit flat items such as prints, cards, jewellery, phone cases and folded clothing. Small Parcel boxes can be up to 450mm x 350mm x 160mm and are used for bulkier goods. Small Parcel postage costs more, so keeping to Large Letter depth where you can saves money on every order.

Are Royal Mail postage boxes recyclable?

Yes. Our postal boxes are plain kraft corrugated cardboard made with recycled content, with no plastic laminate or coating, so they can be recycled kerbside by your customers.

Do the boxes need tape?

The boxes are die-cut with a fold-over lid and side tucks, so they assemble in seconds and hold shut without tape on the base. A single strip of tape or a printed label across the lid is enough to secure them for posting.

Home›Cardboard Boxes›Royal Mail Postage Boxes

Royal Mail Postage Boxes

Royal Mail postage boxes in Large Letter PIP sizes. Flat-packed cardboard postal boxes for cheaper postage. Buy wholesale online, ex VAT.

Royal Mail postage boxes held at 20mm depth to qualify for the Large Letter PIP band
Sizes from 101 x 101mm to 333 x 123mm, supplied flat-packed
Die-cut fold-over lid — assembles in seconds with no tape needed on the base
Strong corrugated kraft board that protects in the postal network
100% recyclable and made from recycled content

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All orders over £150

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Custom sizes & print

Image	Width	Length	Height	PIP Size	Pack qty	SKU	Price Per Pack (Ex VAT)				Quantity
Image	Width	Length	Height	PIP Size	Pack qty	SKU	1-4 Packs	5-9 Packs	10-25 Packs	25+ Packs	Quantity
	101mm	101mm	20mm	Large Letter	50	WCALD0034	£3.50	£3.00Save 14%	£3.00Save 14%	£2.50Save 29%
	112mm	163mm	20mm	Large Letter	50	WCALD0030	£5.50	£5.00Save 9%	£5.00Save 9%	£4.50Save 18%
	123mm	333mm	20mm	Large Letter	50	WCALD0035	£12.50	£11.50Save 8%	£11.00Save 12%	£10.00Save 20%
	159mm	218mm	20mm	Large Letter	50	WCALD0031	£7.50	£7.00Save 7%	£6.50Save 13%	£6.00Save 20%
	220mm	110mm	20mm	Large Letter	50	WCALD0033	£7.50	£7.00Save 7%	£6.50Save 13%	£6.00Save 20%
	230mm	320mm	20mm	Large Letter	50	WCALD0032	£13.50	£12.00Save 11%	£11.50Save 15%	£10.50Save 22%

↑ Click any row to see size diagram, scale reference, and add to cart

Postal boxes sized to Royal Mail PIP bands

Royal Mail prices parcels by size as well as weight — a system called PIP (Pricing in Proportion). Every box in this range is 20mm deep, which keeps it inside the Royal Mail Large Letter allowance of 353mm x 250mm x 25mm, so an item that would otherwise be charged as a Small Parcel can go at the cheaper Large Letter rate. Choose a box that fits your product snugly and the depth does the rest.

Royal Mail size bands at a glance

Royal Mail format	Maximum size	Boxes in this range
Letter	240 x 165 x 5mm	Too shallow for a box — use an envelope
Large Letter	353 x 250 x 25mm	All six sizes below (20mm deep)
Small Parcel	450 x 350 x 160mm	Any of these boxes, plus our deeper mailing boxes

Large Letter postage boxes (20mm depth)

Flat-packed sizes from 101 x 101mm up to 333 x 123mm and 320 x 230mm, all held at 20mm deep. They suit jewellery, cosmetics, phone cases, prints, greetings cards, stationery, small electronics and clothing that can be folded flat. Each box is die-cut with a fold-over lid and side tucks, so it assembles in seconds without tape on the base.

Small Parcel postal boxes

Anything over 25mm deep or heavier than 750g travels as a Small Parcel. If your item will not compress to Large Letter depth, our single wall cardboard boxes and postal boxes with adhesive strip cover that band, and our cardboard postal tubes handle rolled prints and posters.

How to choose the right postage box size

Measure your product at its widest and longest points and add 5-10mm for padding. Pick the smallest box it fits — oversized boxes push you into a higher postage band and need more void fill. If you are shipping mixed products, two or three sizes usually cover most orders. All boxes are plain kraft brown, made from recycled corrugated board and fully recyclable kerbside.

Wholesale pricing drops as pack quantities increase, and delivery is free on orders over £150 ex VAT.