A Guide to Understanding Royal Mail Parcel Sizes | SR Mailing Ltd

A Guide to Understanding Royal Mail Parcel Sizes

Royal Mail has been in existence for well over 500 years, and considering that there are Post Offices and in almost every town across the country, and Royal Mail’s iconic post boxes every few roads, it remains a business that many of us think of as a national institution.

Although Royal Mail has got a lot more competition today, it once held the monopoly on postal services in the UK. There is little wonder then, that when people want to send a letter, a parcel, or a package to someone, whether that is as a personal gift, or because they are a business that is fulfilling an order as a customer, the way that most individuals think of first is Royal Mail.


A Guide to Understanding Royal Mail Parcel Sizes | SR Mailing Ltd


A Timeline Of Royal Mail History


Although it is incredibly well established, the Royal Mail postal service isn’t actually the oldest one in the world – the Egyptian postal service actually dates back to 2000 B.C.! However, with over 500 years of history to the company, there are some interesting points in the Royal Mail history books – we were surprised to learn just how late postcodes were introduced!


1516 – Henry VII knighted the first Master of the Posts, Sir Brian Tuke

1635 – Charles I opened the postal service to the public

1665 – Royal Mail staff totalled just 45 people

1830 – Mail begins being transported by rail

1840 – The iconic Penny Black stamp was introduced

1844 – Numbers of letters sent rose to 242 million, up from just 67 million in 1839

1852 – First pillar box is introduced

1918 – Peak demand during World War One: 2500 staff handled 12 million letters and one million parcels in a week

1959 – Postcode system is introduced

1986 – Royal Mail separates parcel handling, forming Parcelforce

2006 – Royal Mail begins Pricing in Proportion – the biggest change to the system since the Penny Black

2013 – Royal Mail floats shares on London Stock Exchange, beginning the privatisation process


How Many Items Do Royal Mail Carry Each Year?


The Royal Mail Group delivered 9,511 million letters and 1,735 million parcels in the financial year ending March 2021. For those outside the shipping industry completely, that might be a pretty staggering number, but in reality, letters being sent via Royal Mail have dropped from 14,856 million letters in 2017, and parcels are only up by a small amount since then too.


Can I Send Absolutely Anything Using Royal Mail Pricing In Proportion?


Unfortunately, you can’t send just anything, no. There are a wide number of items that are not allowed to be sent via Royal Mail, no matter what size, or weight of the item. There are national and international regulations governing the carriage of mail, and there are a number of everyday items, such as aerosols, nail varnish and perfumes are considered dangerous goods under transport legislation.

Rather than us replicating the list here – because it is long and detailed – we’ll refer you to Royal Mail’s website. For personal customers, you can see the list of items here, and business customers can see the list of prohibited items here.


Royal Mail Parcel Sizes


There are six main sizes of package that Royal Mail stipulate that can be sent within the UK: Letter, Large Letter, Small Parcel, Medium Parcel, Large Parcel, and Tubes. Royal Mail suggest that these are the types of items that can be sent for each type of package:

Letter – Greetings cards, personal letters, postcards, bills

Large Letter – A4 documents, certificates, magazines, CD or DVDs (in their cases), some large greeting cards

Small Parcel – Shoes, portable speakers, mobile phones

Medium Parcel – Gifts, shoes, heavy or bulky items

However, that isn’t where it stops – and there’s a lot more to dig into when understanding Royal Mail Pricing in Proportion. In this next section, we’ll dig into the detail and explain more.

 A glance guide to Royal Mail Pricing in Proportion parcels | SR Mailing Ltd

Royal Mail Pricing In Proportion Standard Letter

Maximum weight: 100g | Maximum length: 24 cm | Maximum width: 16.5 cm | Maximum depth: 5 mm

With a depth of just half a centimetre, the possibilities for sending as a Royal Mail letter size package really does tend to only include paper-based items – perhaps a very small, light booklet at best.  

In terms of marketing, the Royal Mail standard Letter size can still be incredibly useful for businesses, since this size can be used for sending direct mail marketing materials such as special offers on a postcard. However, we suggest that this strategy should be used thoughtfully, since it has a high impact on the environment.

The depth of the standard letter means that most packages sent this way are either paper envelopes, polythene mail bags, or perhaps cardboard envelopes.


Royal Mail Pricing In Proportion Large Letter

Maximum weight: 750g | Maximum length: 35.3 cm | Maximum width: 25 cm | Maximum depth: 2.5 cm

Large Letter is one of the most popular options for businesses that are sending packages via Royal Mail. That’s because, with a Large Letter mailing box, there is actually quite a lot that can be fit into them, despite the fact that the sizing is designed specifically to be able to be posted through a letterbox. Businesses like Hotel Chocolat use them for Happy Birthday chocolates, Marks and Spencer have a whole range of gifts that are letterbox sized (including a delicious Percy Pig one!) and even companies that supply contact lenses are using Large Letter sized boxes.

Not only is there a lot that can be sent inside Large Letter sized boxes, the main advantage for the recipient of the goods is that because it fits through the letterbox, there is less chance of the box being lost when the delivery person finds that the package recipient isn’t at home. This is an advantage for the business too – sending replacements because a courier left it somewhere and someone took it, or it got wet from the rain hits your profits, especially if it ends up happening a lot.

SR Mailing Large Letter Packaging Options

Sr Mailing Small Parcel Packaging Options


Large Letter boxes come in a range of sizes, since the maximum size aren’t always the best option when sending some items. We have a range of options that are suitable for a range of products.

Our range of cardboard Pricing in Proportion boxes suit Royal Mail Large Letter sizing exactly. We have mini boxes, A6 sized boxes, A5 sized boxes, A4 sized boxes, and an alternately shaped Large Letter cardboard box.

Our range of expandable envelopes are sometimes suitable for Royal Mail Large Letter sizing, including the C4L expandable envelope, the C5 expandable envelope. Be careful not to overfill these types of envelopes, otherwise they may expand to the small parcel size.

For plastic mail bags (that are sustainable, of course) to suit Royal Mail Large Letter sizing, our recycled polythene mail bags are perfect, and are available in a range of sizes.

We also have a range of padded bubble envelopes that can be sent as a Large Letter, brown corrugated padded envelopes, and brown kraft honeycomb envelopes.

Of course, if you’re using one of our mail bags, padded bubble envelopes or brown kraft honeycomb envelopes and want to use Large Letter pricing, you’ll need to be certain to measure the depth of the item before sending to avoid additional costs. Just because the package is the correct proportion doesn’t mean that you can go over the depth of just 2.5 cm, unfortunately!


How Can I Tell At A Glance Between A Letter Or A Large Letter?


As a business, it is unlikely that you want to have to grab your ruler or tape measure each time that you send a package – and if you’re not using one of the standard Pricing in Proportion packages or envelopes, that could potentially be on the cards! However, there are many businesses that have produced postal template checkers, and they are available for impressively small cost on many marketplaces. They’re often made from acrylic, in the iconic Post Office red, but our preference is for the wooden ones we’ve seen – because they are far more environmentally friendly.

If you’re unsure whether your item is a Letter size, or Large Letter, you can watch this short video for more information.




Royal Mail Pricing In Proportion Small Parcel

Maximum weight: 2 kg | Maximum length: 45 cm | Maximum width: 35 cm | Maximum depth: 16 cm

Small parcels are an incredibly popular option for ecommerce businesses to send to their customers, since there are so many items that can fit inside Pricing in Proportion Small Parcel boxes. They are also an ideal size for sending subscription service orders through the post – which is why subscription services such as Glossybox use them.

Customers are accustomed to receiving cardboard boxes, they are easy to recycle, since they are nearly always collected by local council refuse services, their strength means that they can often be reused, and they are biodegradable and composable.

Of course, cardboard boxes are not the only option for sending packages via Royal Mail Pricing in Proportion Small Parcel size – larger envelopes, plastic packets and irregularly wrapped items may also be sent in this parcel size category.


SR Mailing Small Parcel Packaging Options

SR Mailing Small Parcel Packaging Options


We have a popular range of cardboard Pricing in Proportion boxes, in mini, midi, parcel sizes, a number of our expandable envelopes that are suitable for sending as a small parcel, as well as several of our book wrap mailers.

Depending on how they are packed and what the package contains, our range of padded bubble envelopes and sustainable plastic mail bags may also be suitable to be sent at Small Parcel rates.


Royal Mail Pricing In Proportion Medium Parcel

Maximum weight: 20 kg | Maximum length: 61 cm | Maximum width: 46 cm | Maximum depth: 46 cm 

When ecommerce businesses are dispatching more than one item in an order, or the products that they are sending are larger, the next size up is the Medium Parcel. Many businesses tend to use the Medium Parcel size for items such as laptops – with the appropriate cushioning, of course! They are much, much deeper than a laptop box of course – 46 cm is over 18 inches, meaning that there is a lot more that can be fit in, without needing to go up to a Large Parcel size.


Royal Mail Pricing In Proportion Large Parcel

Maximum weight: 30 kg | Maximum length: 1.5 metres | Maximum length and depth combined: 3 metres

The very largest packages that Royal Mail handle are sent as Large parcels – those over 30kg, with a length of 1.5m and a maximum 3m length and depth combined. Large parcels that are sent from the Post Office are dealt with by Parcelforce Worldwide.  

Note that if you need to send your parcel via Special Delivery Guaranteed by 1pm®, the weight limit is 20 kg, and for Special Delivery Guaranteed by 9am® it’s 2 kg.


Royal Mail Pricing In Proportion Tubes

For cylindrical items, Royal Mail – perhaps expectedly, given their rather awkward shape – have a completely different way of calculating the price of shipping. The length of the item plus twice the diameter must be less than 104cm, with the greatest dimension less than 90cm. Depending on the size of the item, tubes may be sent as a Large Letter, Small Parcel, or in some cases as a Medium parcel.

If you are planning to send a tube (or a number of them) it is well worth visiting the Post Office, or buy your tube from an expert packaging company to ensure you have the optimal size for your item, and that you don’t inadvertently end up paying more than you need to in order to send the item.

Due to the fact that it tends to be paper-based items that are sent in tubes, strong cardboard is essential – especially for companies that are sending artwork, posters, and maps.


What Else Is Required When Sending A Royal Mail Pricing In Proportion Package?

When businesses are packing boxes to send to their customers, they can’t just pop the item in the box, close the lid and forget about it. There is a need to protect whatever items are in the package, and ensure the delivery personnel can get it to the right place on time. That means taking steps to avoid reports of non-delivery, or return and refund requests as far as possible, which means that cushioning the package, and addressing the package appropriately is essential – as well as considering whether the item should be insured separately.

Cushioning For Royal Mail Pricing in Proportion Packages

When you’re packing products, very often it isn’t as simple as putting the item in the outer package and closing it. Fragile items – and even those that could potentially encounter damage if the package is handled roughly, or accidentally dropped by a delivery person – need cushioning within the packaging.


SR Mailing Cushioning Options

 SR Mailing Cushioning Options

Our range of void fill and cushioning options include sustainable plastic air pillows, pouches and the required inflators, as well as tissue paper, plastic bubble wrap, and honeycomb wrap box and paper rolls. As you’d expect, all of our cushioning products are made from up to 100% recycled materials, and are recyclable, and where possible, are biodegradable and compostable too.


Shipping Labels For Royal Mail Pricing In Proportion Packages

Most businesses, when sending packages to their customers, don’t have the time to write addresses – and not only that, but it also looks unprofessional, and there is far, far too much room for error. Those errors, even if they are only a single letter wrong, can result in the package being delayed, marked as undeliverable, or returned to you, which isn’t ideal for keeping your customers happy.

To avoid handwritten errors, most businesses now use printed labels, which pull shipping information directly from wherever the customer placed the order, whether that is their own website, Amazon, eBay, or somewhere else.


SR Mailing Shipping Label Options


SR Mailing Shipping Label Options


Each business has their own requirements for what a shipping label should look like, and we’ve created a wide range to suit many businesses. We have shipping labels, from one label per sheet, right up to 27 address labels per sheet. We also have self-adhesive polythene wallets with transparent windows suitable to contain delivery notes and invoices, thermal labels on rolls in a range of sizes, and direct thermal label printers available.



If you’re sending valuable items via Royal Mail – especially if you are a business – then you may decide that purchasing additional insurance is a good idea. While Royal Mail are generally known not known for being careless with the packages that they deal with, the sheer numbers that they process each day means that sometimes mistakes or unavoidable incidents occur, and the item is damaged or undeliverable.

The maximum amount of coverage that Royal Mail offer in the UK is currently £2,500. If you’re sending items that cost more than this on a regular basis, then additional coverage may be advisable, or you may look at using a different provider that specialises in handling valuable goods.  


Where Can I Get Packaging That Works With Royal Mail Pricing In Proportion?


Considering that when you’re going to send a package using Royal Mail, you have to have the right size as well as getting the weight right, it makes sense to buy packaging that makes the best use of the sizing requirements. Luckily, as soon as Royal Mail announced the Pricing in Proportion sizing, manufacturers sprang into action and there is now a huge number of packaging solutions that are designed specifically for sending via Royal Mail.

We are a well-known supplier of products for ecommerce businesses, and that you can get packaging suitable for sending through Royal Mail. Not only is our range is affordable, but it is also made from sustainable materials that are either already recycled, or that are easily recyclable or compostable. Our Pricing in Proportion cardboard boxes are made from a minimum of 80% recycled cardboard (usually more) and are durable to withstand impact during transit.

Should I Get Branded Royal Mail Pricing In Proportion Packaging For My Business?

This is a great question, and should be carefully considered. Particularly for ecommerce businesses, there are precious few points of contact between you and your customer, and that means that, to make the best possible impression on your customer, you need to think carefully about each possible interaction. Branding postal packaging isn’t right for every business, however – for businesses that are selling intimate, or personal care items, customers may prefer plain packaging. You probably don’t want your local delivery driver (or your neighbours, if they take the package in for you!) to know that you are ordering products from a sexual wellness company, for example – and your customers are the same.

It has been shown that poorly packaged goods are much more likely to request a return or refund, and that will cost your business, not just in terms of time to process the return, but also because customers are more likely to complain. Complaining directly to you is one thing, but when they voice their annoyance on social media, or on review websites, that starts to damage the reputation of your business, and can have an impact on whether customers in the future decide to buy from you.

By applying branding to high quality Royal Mail Pricing in Proportion boxes, you’re helping to increase brand recognition each time a package arrives with a customer. There are so many businesses that apply their branding to their packaging today – from Amazon’s instantly recognisable simple brown cardboard boxes with their arrow logo, to Specsavers sending contact lenses by post, and many more.   

First impressions aren’t the only reason to apply branding to your packaging though. Branded packaging shows your customers that you care what they think about your company, and it provides a much more luxurious look and feel when they receive their order – making them feel special.

In addition to creating a great impression on your current customers, there are an increasing number of people creating ‘unboxing’ videos on their social media means that it can be much, much more than just the customer that you dealt with that sees your packaging. Those watching unboxing videos may decide to shop with you purely on the basis of that video, making the increased cost well worth it.

While there is an increase in cost to produce bespoke packaging, when compared with unbranded, it is well worth it. The extra cost is returned in terms of increased brand awareness and repeat custom, which can help to further increase your profits. We can produce bespoke boxes, mail bags and packing tape, at a price that makes sense – and many of the businesses that we work with to produce those packages agree that it has helped create a strong impression of their business.

If you don’t have the time, or the resources available to create the design you want for your Pricing in Proportion packaging, you can still access it! Our expert design team are available to work with you, and will aim to completely understand your business and your customers, before they set to work. Their aim is create designs that clearly convey what your business is and does, that stand out from the rest of the boring plain brown packages, and that both you, and your customers will love. Contact us with the requirements of your business, and to discuss what we can offer.


How To Estimate Package Weights


As we frequently find when we’re trying to establish how heavy our suitcase is when we’re going on our holidays, estimating how much something weighs is often pretty tricky, especially if you don’t have scales that can provide accurate measurements. With that in mind, the team at Royal Mail have provided the following guidance to help us with our estimates.

Letter or greeting card - 30g

Standard DL (110mm x 220mm) envelope with 4 sheets of A4 - 44g

A4 envelope with 20 sheets of A4 - 160g

Mobile phone in bubble envelope - 180g

400 page paperback book in bubble envelope - 310g

Pair of jeans - 500g

Glossy magazine in bubble envelope - 585g

Pair of trainers - 1kg

Businesses that are sending parcels regularly should definitely have their own set of scales on site – and perhaps even several! These are widely available and relatively inexpensive to purchase, and are well worth the investment.


Sending Parcels Via Royal Mail To Countries Outside The UK


It goes without saying that the further you need to send a parcel, the more it is likely to cost – and that is true for all postal and courier services around the world. Royal Mail international letter and parcel services are no exception, and you can find the prices with much more information – including whether you need the package tracked, and signed for – with international business shipping costs here.


How To Calculate Shipping Costs


Costs for sending packages can differ vastly between shipping services, and like Royal Mail, many couriers consider the size, and the weight of the package, as well as where the package is being dispatched from, and delivered to. There’s also usually a price difference when it comes to the speed that the package needs to be delivered – with the slowest services normally cheaper, and the fastest the most costly. Sending a package from Scotland to Cornwall by 9am the next day is definitely possible, but it will cost you!

There are other costs to consider when you’re sending a package too though. Do you need to be able to track the package – or maybe your customer does? Do you need the package to be signed for on receipt? Are the content of the package valuable? If so, do you need additional insurance?

It can all get pretty complex, pretty quickly, and so a lot of individuals tend to stick with Royal Mail, simply because it means that they can pop into their local Post Office and get the answers they need, face to face. However, there is a lot of competition for courier services, and so here are links to shipping calculators and the costs for sending with each company.  

Royal Mail







What Are The Alternatives To Royal Mail?


There are actually countless alternatives to Royal Mail, if you consider how many independently run courier services that there are, and local companies. However, there are a number of big players in the delivery industry here in the UK.

For letters, there are six main companies that compete with Royal Mail: Whistl, TNT (soon to become FedEx Express), UK Mail, The Direct Mail Company, Citipost Mail, and Digi-Mail.

For other packages, then there are a range of companies that compete with Royal Mail: DPD, Hermes, DHL, UPS, FedEx, and TNT.


Which Company Is The Best Courier In The UK?


There’s a lot of discussion about which company is the best for sending parcels in the UK – and really, most people are influenced by the service they receive, meaning that if they have one or two bad experiences, they’re likely to be vocal about them. It only takes one bad day to colour someone’s opinion, so bear that in mind when you’re reading reviews.

Research has shown that the most popular courier and shipping services for online stores are:

Click and collect – 52.9%

Royal Mail – 31.9%

DPD – 30.2%

Hermes – 23.1%

DHL – 9.2%

While this is an indicator of which services are the favourites, they might not be right for your business – so be sure to do your research carefully.

Is Parcelforce Part Of Royal Mail?

Parceforce is indeed part of the Royal Mail Group. In 1986 Royal Mail separated parcels out, into Royal Mail Parcels, so that dealing with parcels was a completely separate operation. It was rebranded in 1990 as Parcelforce, and rebranded again in 1998 to Parcelforce Worldwide.

The company has 54 depots across the UK and The National Centre can handle up to 58,500 parcels per hour. During peak times, they take delivery of a fully laden vehicle every 45 seconds – so it is safe to say that they are pretty busy.


Which Is The Best Courier For Ecommerce Businesses?


If you’re searching for the best courier for ecommerce businesses, this question is even more tricky to answer, since the size and weight of the different packages that you have may influence which is the best shipping service for your business. You may even find that more than one service is right – especially if you’re sending products to customers overseas. Because of the complexity of choosing the best service when you’re dealing with a large number of different sized and shaped parcels, many businesses are turning to shipping consolidator services, that can get the best deal for you on each and every parcel.


What Are Shipping Consolidator Services?


Also known as multi carrier services, consolidator services collect parcels from hundreds (if not thousands) of local businesses and then get the best possible rates for each parcel. Just as buying products in bulk means that you can access a much better rate, because consolidators send so many parcels through each service, their buying power means that they can access much better rates for the businesses that they serve. It is often known as ‘pooled volume’ and alongside the software that these services often provide, can be really beneficial. 

Because they work directly with the carriers – more than 20, in some cases – they also know which services are right for the sizes and weights of packages that you’re sending.

Consolidator services are also able to do business collections, and although Royal Mail can provide this type of service for businesses, it will cost you – unless you’re spending more than £16,500 a year on postage. Having a consolidator service collect your packages means that your team can work more effectively, and you don’t need to spare a member of your team to take your packages to the collection office.

If all this sounds good to you, then a great place to start is by checking out what Parcelhub, ShipStation and GFS have to offer – they all have their own merits, so be sure to establish which one is best for your business.


A Guide to Understanding Royal Mail Parcel Sizes


Our Final Thoughts


Royal Mail is a well-loved, national institution, and there will always be people who choose to use them for sending absolutely anything by post. However, for some businesses – and indeed, some individuals – Royal Mail isn’t the right solution for sending packages, whether that is due to the sizing restrictions, the pricing, or a different reason. Luckily, there are plenty of other shipping companies and couriers that are suitable to work with.

Whatever you’re sending, we believe the main thing – as you might expect us to say, given our mission – is that whenever we’re sending packages by post, we choose the most sustainable options. To find those, head to our Postal Packaging page, and to discuss the packaging solutions that you need for your business, get in touch.


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quality packaging on 2023,06,15

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Francesca Bartlett on 2023,03,06

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Robbin Bachus on 2023,03,06

Hello srmailing.co.uk admin, You always provide clear explanations and step-by-step instructions.

Roxstech on 2022,05,19

The tubed packaged goods (TPGs) are a type of packaged food that is usually sold in a single-use plastic container. They are commonly found in supermarkets, health food stores, and drugstores.
What are tubed packaged goods? Types and its Advantages

Kun Feng
Kun Feng is the foremost sustainable packaging expert who possesses the fundamental eco-knowledge and passion necessary to drive new levels of eCommerce growth without compromising people, the planet, or the economy. 

As the co-founder and managing director of SR Mailing, He has successfully helped over 9,000 eCommerce businesses transform into sustainable suppliers and takes pride in being able to offer eco-friendly packaging solutions that bolster eCommerce reputation and scalability, all while supporting the bigger picture along the way.

Feel free to contact with Kun on Linkedin or Facebook
Kun Feng

Managing Director