The UK Guide to Custom Mailer Box Sizes & Specifications
Custom mailer boxes are the industry gold standard for UK e-commerce brands, subscription boxes, and luxury retail dispatch. Built from self-locking corrugated cardboard (FEFCO 0427 style), they require no packing tape to assemble and deliver an exceptional unboxing experience.
Standard UK Mailer Box Dimensions & Postal Brackets
| Box Size (L x W x D) | Royal Mail PiP Category | Ideal Product Application | MOQ |
|---|---|---|---|
| 220 x 160 x 20 mm | Large Letter (Qualifying) | Jewellery, cosmetics, phone cases, lettersbox gifts | 50 Units |
| 250 x 200 x 70 mm | Small Parcel | Skincare bottles, perfumes, candle sets, t-shirts | 50 Units |
| 310 x 230 x 100 mm | Small Parcel | Apparel, knitwear, shoes, curated gift hampers | 50 Units |
| 380 x 280 x 120 mm | Medium Parcel | Multiple garments, homeware, electronic gadgets | 50 Units |
Choosing the Right Board Thickness: E-Flute vs. B-Flute
- E-Flute Corrugated (1.5mm Caliper): Excellent surface smoothness for crisp photorealistic CMYK digital and litho printing. Rigid yet lightweight, perfect for subscription boxes and cosmetic kits.
- B-Flute Corrugated (3.0mm Caliper): Superior stacking strength and puncture resistance. Recommended for heavier goods, glass bottles, and bulk transit.
- Kraft vs. White Coated Liners: Unbleached brown kraft provides an authentic, rustic eco-friendly feel, while clay-coated white liners make vibrant brand colours pop.
Order a Free QPack Material Sample Pack to test our board thicknesses, print finishes, and dielines before placing your full production order.
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QPack Packaging Engineering Team
London-based packaging specialists engineering bespoke mailer boxes, folding cartons, kraft paper bags, and sustainable food packaging solutions for UK brands.