The wrong box costs you money on every single shipment — in wasted materials, dimensional weight fees, and damaged product returns. Here's how to spec the right mailer or shipper box for your e-commerce operation.
Most e-commerce brands ship in one of two formats:
- Mailer boxes — rigid, custom-printed, self-locking boxes that fold flat for storage. Best for lighter products, apparel, beauty, and anything where presentation matters.
- RSC shipper boxes — the classic brown corrugated shipper. More protective for heavier or fragile products. Can be printed on the outside for brand visibility.
Canada Post, Purolator, UPS, and FedEx all charge based on dimensional weight (DIM weight) — not just actual weight. DIM weight is calculated as: Length x Width x Height / 5,000 (in centimetres). If your box's DIM weight exceeds its actual weight, you pay the DIM rate.
This means oversized boxes cost you money even if your product is light. The fix: spec your box as close to your product dimensions as practical. For more on e-commerce packaging, see our E-Commerce industry page.
Mailer boxes are measured by interior dimensions: Length x Width x Depth. Always spec based on what needs to fit inside, not the outside of the box.
- E-flute corrugated: Lightweight, good crush resistance, excellent print surface. The most common choice for e-commerce mailers.
- B-flute corrugated: Thicker, heavier, more protective. Better for fragile or heavier items.
- Rigid paperboard: Premium feel, excellent print quality. Used for luxury unboxing.
For consumer brands, the box is part of the product. Custom printing on the outside creates a brand moment at the doorstep. Printing on the inside lid creates a second surprise moment on open. Also see our guide to custom packaging costs to budget your e-commerce packaging.
- Measure your product at its largest point (including any packaging it arrives in)
- Add 1-2 cm clearance on each dimension for void fill or tissue
- Check the DIM weight of your target box size with your carrier
- Decide whether you need interior printing or just exterior
- Order a small run first to test before committing to larger quantities