Royal Mail Postage Boxes

Why should I optimise my eCommerce packaging for Royal Mail postal sizes?

The steady rise of e-commerce has seen something of an explosion, fuelled by the consequences of recent events. The bricks-and-mortar retail experience involving face-to-face interaction is fast being overtaken by the virtual, where your website and packaging become the main players in your customers’ shopping experience. In fact, 55% of customers would not recommend a poorly designed website that’s not optimised for mobile to their peers. Think about that! The online customer has come to expect a curated online experience and for mail-ordered goods to arrive in a presentable fashion and when promised.

Next, taking the time to research and optimise the design and style of packaging and presentation can result in the most exciting unpacking experience, potentially adding to the number of favourable reviews on your nicely optimised website. So what’s the impression of the parcel you sent them?  Is it one of care for the customer, the product and the environment? Is it easy (or fiddly) to open for a start? Using packaging that is over-bulky or difficult to recycle won’t earn you brownie points. Can they easily re-use it to return any items not needed – or worse still – damaged?

Ecommerce returns in the US in the 2018 holiday season came to £32 billion – up to 30% of that was due to damaged items. Making sure your protective packaging does what it needs to, protect its contents – and your customers’ much-awaited delivery – is imperative. Especially when we can reveal that returning customers spend up to 67% more than first-time customers. Damaged goods mean a damaged customer relationship

Packaging – the new customer interface

Many items such as clothing, books, home goods and electronic items require protection from moisture for example, so polythene wrapping would probably be on your packaging wish list. But you don’t need to lose sight of eco-friendly options here. There are polybags made from recycled materials as well as some paper packaging with splash resistant coatings. Other items might need void fill and again, you don’t have to turn to plastic bubble wrap for this, there are plenty of eco-friendly void fill options available. We’ll be looking at this in greater detail below.

Right now, businesses finding themselves under increasing financial pressure will no doubt be looking at all ways to reduce costs. And a simple thing such as optimising for postal sizes can deliver cost-saving benefits.

Thinking about your products and how to get them safely to your customers and looking good will be your priority. But you also want to make sure anything you send is cost-effective and optimised for the Royal Mail postal sizes. So let’s take a look at making the most of this new face-to-face with your customer.

Your guide to Royal Mail postal sizes categories

Royal Mail Letter

With the Royal Mail Group having delivered around 10 billion addressed letters during the twelve months ending March 2020, this is the volume end of the postal categories.

Maximum weight is 100g and size up to 24cm x 16.5cm x .5cm.

This includes popular DL and C5 envelopes, and also the first 3 sizes of light bubble bags and various CD/DVD mailers


Royal Mail Large Letter Boxes

Maximum weight is 750g, 35.3cm x 25cm x 2.5cm.

Paper padded envelopes

This includes envelope sizes up to C4 and B4 and similarly the first 5 sizes of padded bags. Again, you can still hang onto your green creds with paper padded envelopes that don’t have a plastic bubble but provide equal protection. Where the contents are heavier then stronger padded bags offer greater protection such as Gold Jiffy padded bags.

Customers will appreciate packages being of a size that can be readily posted through a standard letterbox where possible rather than run the risks associated with leaving goods outside the door.  There is scope to improve your delivery costs by ordering your own bespoke packaging to keep you within the appropriate size constraints. Single wall corrugated cartons of various styles can make for a light protective package.

The incentive to pack wisely within this category is that the next step up, whilst permitting almost 3 x the weight does so at 3 x the price!  Why not use some of the money saved from paying the next tariff up to custom print your packaging, reinforcing your company branding?

Royal Mail Small Parcel Boxes

Maximum is 2kg, 45cm x 35cm x 16cm.

Corrugated book wrap mailer

Generally, cartons and mailers, both padded and unpadded will be the popular choice here. There may be more need for simple protection and void-fillers unless you have a range of carton sizes or padded bags at hand. Consider nesting or telescopic cartons to accommodate fluctuating contents.

Worthy of special mention is the corrugated book wrap mailer.  Not exclusively for books, they come flat and makeup speedily using pre-creased folds, providing corner protection and rigidity in a lightweight package.

Royal Mail Medium Parcel Boxes

Maximum is 20kg, 61cm x 46cm x 46cm.

Soft furnishings and clothing generally travel well in self-seal polythene mailing bags. Not only are they lightweight, but there is a further bonus of being water-resistant. Used appropriately, paper sacks could replace polythene sacks. Another solution could be looking at the ‘multi-scored cartons’ so that the box height can be more easily adapted to suit the contents as well as reducing the need for void-fillers. This gives you so much more flexibility, especially if you have a range of different sized products.

Royal Mail Large Parcel Boxes

Maximum is 30kg, 150cm x a combined width and depth of 300cm.

Here the potentially greater weight will necessitate the use of cartons constructed from double-walled corrugated cardboard. If the products inside are heavy, sharp and could work their way out of a carton, then fitments made of corrugated, film or foam may be required to hold the goods in place.

Do check the Royal Mail website re-weight restrictions on Special Delivery items on postal sizes.

Internal Dimensions vs External Dimensions – A Crucial Consideration For Royal Mail Postage Boxes

When speaking to box manufacturers about eCommerce packaging that needs to fit within a specific Royal Mail size restriction, please be aware of the confusion that often occurs over the internal and external parcel dimensions.

Box manufacturers, almost without fail, will always quote you for the internal size of the box.  This is because the entire packaging manufacturing industry is heavily standardised, for example, they all prefer to use the EU standard FEFCO codes to describe standard box styles.

The end-users of e-commerce packaging, however, typically prefer to use external box dimensions – especially when trying to align with Royal Mail postal sizes which are all external dimensions.

So there you have it – the perfect setup for rejected batches of custom made packaging: the customer thought they were going to receive a box with maximum external dimensions of H x L x B, and the manufacturer thought they were making a box with minimum internal dimensions of H x L x B.

This is especially crucial if you’re trying to fit within the large letter size which has a mere 25mm thickness allowance, and when using thicker grades of corrugated card.  For example, in the corners where 3 layers of card may overlap at the seams, a cardboard thickness of just 2mm can create a 6mm difference on each side, so up to 1.2cm overall too large.

Then squeeze a bulky item inside the package that makes the card bend out slightly and you’re even more likely to find you’re over the size limits.

Manufacturers Box Size Tolerance

Another word of caution when ordering bespoke size boxes for e-commerce – manufacturers typically have a + or – tolerance of several millimetres, 5mm tolerance is not uncommon.

This means that going to the maximum size you think you can get away with within Royal Mail limits is risky for bespoke size packaging – especially if you are a larger user (Royal Mail tend to be more lenient on low-volume clients than high-volume users who may be penalised for just 1mm oversize).

Check the box size tolerance before you order.  Typically Die-cut boxes and boxes on thinner card such as E-Flute will have less size variation from one batch to the next than boxes that are CAD-cut or else made from thicker grades of card like B-Flute or EB-Flute for example.

Choose eco-friendly Royal Mail postage boxes

Reduce, Reuse, Recycle.

What does this have to do with postal sizes? Well, we all want to be seen to be ‘doing our bit’ for the environment. Your customers are very interested in your ‘greener’ packaging choices! We need to Royal Mail Postage Boxes practice the above principles whilst keeping close control on costs. By all means, weigh-up the pros and cons by following our suggestions below. Keep one eye on the Royal Mail dimensions, a cheap (free) box that unnecessarily puts you in the next postal sizes charging bracket will cost far more than buying your own bespoke size in the long run.

Ensure that your packaging is fit for the purpose. Common sense isn’t it? Well, yes. But rather than taking any old box or wrap, it is worth checking if the packaging could be lighter, tighter and thinner where you are sending numbers of unbreakable items. Could you use a smaller box and save wastage? Or even use a mailbag or book wrap instead of a small box  >2kg with a maximum size of 45cm x 35cm x 16cm.

Matching box sizes to popular order sizes will reduce the amount of filler required to prevent the contents from knocking around inside. When on the receiving end of goods in oversize cartons, the unboxing of copious amounts of void fill can be an irritation. So think about the likely reaction of others to your finished article, but also think of the environmental impact of the way you pack.

Packaging Machinery

Paper void fill

Rather than send polystyrene shapes that will end up blowing around the client’s floor and car park, you could use alternatives such as paper to fill voids and protect the goods in transit. There are several machines that will stand ‘in-line’ beside the work-station and deliver scrunched-up paper or pads on demand, usually from a compact roll and driven electrically.

For the smaller user, then rolls of corrugated paper can work well to protect and stabilize the Royal Mail postage boxes contents via block and brace. Corrugated rolls can be supplied in numerous standard widths and are made of nearly 100% recycled paper.

If padding is not required, then sacks are a good option. The choice then is to go for a paper sack, which is robust but not totally waterproof, or a plastic sack which is water-resistant without offering any stiffness or padding.

Paper Tape

Which brings us to the question of sealing tape. Whilst the market went overboard for plastic tape and away from gummed paper tape 50 years or so ago, the environmental argument against the majority of plastic tapes is pretty clear when it can interfere with the straightforward recycling of corrugated cardboard boxes and paper that still have plastic tape attached. So what to do? Maybe you are prepared to invest some time looking into the benefits of paper tape and dispensers.

Dispensers for gummed paper tape start around £40 for a basic and go into many £hundreds for the electric variety. These are quick to use and present you with precise, pre-set lengths of ready-to-apply paper tape at the touch of a button.

The alternative, which is becoming popular with both small and large users, is the self-adhesive paper tape in sizes and units that mimic plastic tapes and use similar adhesives. Paper tapes blend in discreetly on corrugated and paper packaging. A word of caution here: paper tapes have a lower burst tolerance than most plastic tapes, so a reinforced paper is needed for sealing heavier packages.

Various Die-Cut Postal Cartons 

Popular in but not limited to Small Parcel Category. Clever little cartons that are lightweight, some are self-locking so don’t require tape for sealing and assemble in seconds. A great choice for fragile items which look neat and stylish too.

Maximum is 2kg, 45cm x 35cm x 16cm

Keeping within the limits of the various Royal Mail postal boxes sizes classifications is made simple by using either standard or bespoke fold-up cartons. With a useful variety of styles available, choose whatever suits your operation. It’s not hard to use a green solution for your packaging. Just don’t be put off by the number of different options. Get to know your priorities and speak to a packaging expert who can guide you through to a great outcome.

Time spent experimenting may be repaid many times over through savings in postage costs. Learning how to optimise your packaging to fit postal sizes that looks great as well as protecting each delivery will certainly help you win over customer loyalty. It can be done!

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