The Complete Guide to Letterbox Packaging for Online Sellers
The definitive guide to letterbox packaging for UK e-commerce businesses.
What is letterbox packaging?
Letterbox packaging is designed to fit through a standard UK letterbox, qualifying for Royal Mail large letter postage rates. It is the single most effective way for e-commerce businesses to reduce shipping costs on eligible products while guaranteeing first-time delivery.
Quick answer
Letterbox boxes must stay under 353mm x 250mm x 25mm and 750g to qualify for Royal Mail large letter rates. They save £2-3 per shipment vs small parcels, eliminate missed deliveries, and store efficiently. Choose the right size for your product, add minimal branding to start, and scale to custom printing as your business grows. Most small e-commerce products under 25mm thick are candidates.
Key benefits
Large letter from 93p vs small parcel from £3.35.
No missed deliveries, no depot collections, no customer frustration.
A snug letterbox box feels intentional and premium.
Thinner packaging uses less cardboard and generates less waste.
Royal Mail rules
Large letter maximum: 353mm x 250mm x 25mm, up to 750g. Four weight bands with increasing prices: 0-100g, 101-250g, 251-500g, 501-750g. Exceeding any dimension by even 1mm reclassifies as small parcel.
Deep dives: Royal Mail rules or sizing guide.
Choosing your box
Selection steps0 / 4 checked
Branding options
Start with a branded sticker on plain kraft for the lowest cost entry. Progress to single-colour printing at 500+ units, then full-colour digital at 100+ units. Inside printing and tissue paper add premium unboxing touches. Every letterbox delivery is a brand touchpoint - make it count.
Start with letterbox boxes
Stock and custom letterbox boxes from ProcuraPack. Samples available.
Browse letterbox boxesFrequently asked questions
Thin packaging (under 25mm) designed to fit through a letterbox and qualify for large letter postage.
£2-3+ per shipment by qualifying for large letter rates instead of small parcel.
Jewellery, phone cases, cosmetics, stationery, seeds, and any item under 25mm thick and 750g.
No, start with plain boxes and branded stickers. Add printing as volume grows.
Measure your products, order sample boxes, test-pack and test-post, then order in bulk.
Part of our guide
Product Guide: Letterbox Boxes
Expert guides on letterbox packaging, from sizing and Royal Mail rules to branding and sustainability.
Browse all guides →
