Shipping guide
Courier Packaging Guide
Royal Mail, Evri and UK courier size guides explained – so you can pick the right box, avoid surcharges and keep shipping costs predictable.
Why box size matters
Choosing the right box size
Choosing the right box size isn’t just about fit, it directly impacts your shipping costs, delivery success, and risk of surcharges.
This guide helps you align your packaging with Royal Mail, Evri, and courier size categories so you can standardise packing, avoid pricing jumps, and scale efficiently.
Box checker
Find out your shipping costs
Choose the right box and avoid unnecessary shipping costs.
Simply enter your package dimensions to see which Royal Mail or Evri size category your parcel falls into. Compare courier size bands, identify suitable box options and make more informed packaging decisions for every shipment.
Size guides
Royal Mail & Evri size guides
Royal Mail
Size bands – what you must stay within
Letter
Documents only
240 × 165 × 5mm
Large Letter
Flat e-commerce, clothing, books
353 × 250 × 25mm
Small Parcel
Small boxed goods, shoes
450 × 350 × 160mm
Medium Parcel
Multi-orders, bulkier items
610 × 460 × 460mm
These sizes are fixed – there’s no flexibility.
Evri
More flexible – but not unlimited
Evri pricing is weight-led, but size still matters.
Letterbox-friendly / Postable
Ideal for subscription boxes and low-value items
~350 × 230 × 10–30mm
Max length
Standard & large parcels
1200mm
Max combined size
Standard & large parcels
2450mm
Max weight
Standard & large parcels
15kg
Go beyond these and you’re into surcharge territory.
Free download
Take the guesswork out of shipping
Before you ship
Choosing the right box
Before finalising your packaging, check:
- Are you using external dimensions (not internal)?
- Have you added a packing allowance?
- Is there unnecessary empty space increasing your size?
Just as importantly:
- Oversized boxes increase costs
- Overfilled boxes increase dimensions
- Ignoring depth (especially the 25mm limit) causes instant price jumps
Why this approach works
By working through this process:
- You remove guesswork from packing
- Your team can pack faster and more consistently
- Your shipping costs stay predictable
- Scaling becomes much easier
Ultimately, the right box size doesn’t just protect the product – it improves your entire fulfilment workflow.