Understanding Royal Mail Parcel and Letter Sizes: Comprehensive Guide for Ecommerce


royal mail parcel size

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Royal Mail is a trusted UK-based courier company that offers a wide variety of parcel and letter sizes that suit different ecommerce business needs. 

Whether you are shipping from the UK internationally or locally, Royal Mail is available in support of UK-based ecommerce. 

This article provides an overview of the different options Royal Mail offers for parcel and letter sizes.

Overview of Royal Mail parcel services

With a rich history that spans over 500 years, Royal Mail is one of the oldest parcel services companies in the world. It currently offers parcel and letter services for items of different sizes.

You will see in the table below, a quick overview of the maximum dimensions of Royal Mail’s courier services.

FormatMaximum weightMaximum lengthMaximum width
Small Parcel2 kg45 cm35 cm
Medium Parcel20 kg61 cm46 cm
Large Parcels30 kg2.5 mN/A
Letter100 g24 cm16.5 cm
Large Letter size750 g35.3 cm25 cm
TubesEnsure that length + (2 x diameter) < 104 cm, and the greatest dimension is < 90 cm.

Royal Mail Small Parcels

These small parcel boxes came in many variants that can go up to 45 cm x 35 cm x 16 cm in size. And it allows for items with a maximum thickness of 1.6 cm and up to 2 kg in weight.

Medium Parcels

Royal Mail medium parcels refers to packages that are as large as 61 cm x 46 cm x 46 cm, and up to 20 kg.

Large Parcels

Royal Mail large parcels refer to packages that are up to 2.5 m in length or up to 30 kg would need to be shipped via Royal Mail large parcels. This is sent via ParcelForce Worldwide, a part of Royal Mail.


If you have a letter of maximum size 24 cm x 16.5 cm x 0.5 cm (length x width x thickness) and up to 100 gm weight, you can use Royal Mail letters. Both, first and second class letter sizes are the same.

Large Letter 

With Royal Mail large letters, send large letters that are a maximum size of 35.3 cm x 25 cm x 2.5 cm (length x width x thickness) and not weighing more than 750 g.


This is used for goods that weigh up to 2 kg, with length up to 90 cm and length plus twice the diameter not more than 104 cm.

Here is an overview of the costs associated with each Royal Mail service:

Royal Mail Size TypesWeight up to:Price
Small Parcel2 kg£3.49
Medium– 2 kg
– 10 kg
– 20 kg
– £5.49
– £6.99
– £10.49
Tube– 100 gm to 2 kg
– 5 kg to 10 kg
– 15 kg to 20 kg
– £4.49
– £5.99
– £9.49

Comprehensive guide to Royal Mail parcel sizes

Below are a few examples of parcel sizes and prices when shipped via Royal Mail (not all of which can be fulfiled by ShipBob, but are used for illustration purposes):

ItemDimensionsWeightRoyal Mail serviceRoyal Mail pricing starting from (for shipping within the UK)
A book22.9 cm x 15.2 cm 142 gmSmall parcel£2.99
A canvas50 cm x 50 cm1 kgTube£4.49
A violin for kids33 cm  500 gmMedium parcel£4.49
A chair175 cm x 80 cm30 kgLarge parcel£54.33
A laptop38 cm x 26 cm4 kgMedium parcel£5.99

A few notes:

  • Small items like jewelry, books, and novelty candles would fit into a small parcel. 
  • Medium items like clothes, shoes, laptops (bigger than 33 cm and heavier than 2 kg), and kitchen appliances would require a medium parcel.
  • For large items like furniture and sports equipment, that weigh more than 20 kg, you would need to choose a large parcel.
  • Irregular-shaped items like musical instruments and artwork could also be sent with large parcels.
  • If you wish to send a canvas or reams of paper, you could use the tube.

Overall, Royal Mail’s shipping costs fluctuate significantly with changes in the weight of the package. If you were to ship a dumbbell weighing 2 kg, it would cost only £5.49 by medium parcel service. 

But an 8 kg dumbbell would cost £6.99 and a 14 kg one would cost £10.49 to ship within the UK.

The price also varies with the geography that the packages need to traverse. For example, if you were to ship a book weighing 2 kg to the mainland USA from the UK, it would cost £14.30. Whereas it would only cost £2.99 for shipping within the UK.

The costs are also different based on the urgency of the order shipment. Shipping the book of 2 kg can cost £10.85 within the UK with special delivery guaranteed by 1 pm.

There are also different prices for next day delivery, delivery with signature, delivery with age verification, and so on.If you are transporting expensive goods, you can even choose coverage up to £2,500 at an added cost.

Understanding Royal Mail letter sizes

Letters can be up to 100 gm and maximum size of 24 cm x 16.5 cm x 0.5 cm. This service is used for greetings cards, postcards, or bills.

You can also send large letters with a maximum size of 35.3 cm x 25 cm x 2.5 cm, and weighing up to 750 gm. Use this service to send certificates, magazines, documents, and CDs.

Royal Mail SizesWeight up to:Prices
Letter100 gm£ .75
Large Letter – 100 gm
– 250 gm
– 500 gm
– 750 gm
– £1.15
– £1.85
– £2.40
– £2.70

Understanding the cost implications and packing guidelines

As the parcel size increases, so does the cost of shipping.

Here are Royal Mail’s specific rules and regulations about packaging:

  • With the parcel, you must include a barcode and full destination address (including post code), a UK return address, and a complete sales order.
  • Padded envelopes or mailer bags are necessary for items with sharp edges or odd shapes.
  • Take permission from Royal Mail before using wallets, tape, string, or strapping on a parcel.
  • The writing on the shipping label must be clear and legible.
  • Place one address label outside and another inside the package.
  • With small packages, make sure that the barcodes and address information aren’t wrapped over the edges.
  • Avoid placing sticky tape over the label.
  • Use a thermal printer when printing your own shipping labels. And they need to be designed using Royal Mail approved software.
  • If you have multiple fragile items in a package, make sure they don’t touch each other or the side of the box.
  • As necessary, include cushioning materials (especially so for fragile goods) and book wrap, or bubble wrap.
  • Close all edges and open areas with packing tape.
  • For easily breakable goods use a ‘FRAGILE’ sticker.
  • Depending on the service you choose, you may be required to weigh each item or put them into a sealed bag. Find out the details here.

For efficient and safe packaging, at ShipBob we recommend that you follow these steps also:

  1. Select a service that suits the dimensions and weight of your item.
  2. Use strong tape and appropriate labelling.
  3. Consider the environment when packing your order items. It may help to choose biodegradable packing material. Also, distribute your SKUs to fulfilment hubs closest to your customers for more efficient last-mile delivery.

How ShipBob can help with your Royal Mail shipments

Royal Mail delivers 650+ million parcels each year. Is that your preferred courier company for shipping from and within the UK? 

Then we have good news, ShipBob works with this courier company to streamline your entire order fulfilment process. 

Thanks to the direct integration between ShipBob and Royal Mail, you also stand to lower shipping costs. We also offer access to real-time carrier rates that can be shown on your ecommerce platform to improve delivery expectations and exceptions.

Sometimes you may want to try other courier companies. But it can be a struggle to compare the services of Royal Mail vs DHL, DPD vs Royal Mail, etc. 

ShipBob weighs the pros and cons of these shipping companies on your behalf and assigns the best courier services to meet your business needs, so you can focus on growing your company.

“Before ShipBob, we were fulfiling all of our UK orders out of our Oxford office, with one person in charge of picking and packing orders and taking them to Royal Mail daily. This solution was not scalable, especially if we wanted to continue expanding our business into new countries and demographics.

We knew we needed a partner with a global presence, who could handle fulfilment for us wherever we go. Thankfully, ShipBob has fulfilment centres in strategic locations not just across the US, but all over the world. We’re able to store inventory on both coasts of the US and in the UK and Poland, which cuts our average shipping costs and shipping times considerably.”

Natalia Lara, CMO of Oxford Healthspan

Royal Mail parcel size FAQs

Below are answers to the most common questions about Royal Mail parcel sizes.

Is Royal Mail strict on parcel size?

Yes, you need to adhere to the parcel sizes offered by Royal Mail to ensure that your packages are accepted and processed efficiently.

How does Royal Mail define ‘small parcel’?

Any package that is less than 45 cm x 35 cm x 16 cm in size and up to 2 kg in weight can be classified as a small parcel.

What is the maximum weight for a medium-sized parcel?

The max weight of a medium-sized parcel would be 20 kg.

How do I know if my item qualifies as a ‘large letter’?

Royal Mail large letters can accommodate items that are a maximum size of 35.3 cm x 25 cm x 2.5 cm (length x width x thickness) and not weighing more than 750 gm.

How do I correctly measure my parcel or letter?

  1. Measure the length, width, and height of the item.
  2. To arrive at the girth of the package, you must add the two smallest dimensions and multiply the result by two.
  3. To know the combined length and girth of your parcel, add the longest dimension to the package girth. 

What happens if my parcel exceeds the size limit?

Typically your package is measured at the post office or Royal Mail counter and billed accordingly. In case your parcel significantly exceeds the size or weight limit, it will be delivered but the recipient may have to pay the calculated excess postage.

Can ShipBob handle oversized items?

It is difficult and expensive to pack and ship these oversized goods. Luckily, ShipBob knows the rules that each carrier uses for oversized packages. 

So you can always choose the most affordable option. We also help you get the best deals for your big parcels thanks to our relationship with different couriers when shipping from UK

How does ShipBob’s return management work with Royal Mail?

Thanks to ShipBob’s partnership with Royal Mail, you get access to seamless returns and more efficient reverse shipping options. The moment an order return request is placed and accepted, ShipBob works with Royal Mail to quickly pick up and deliver the returned goods to the nearest fulfilment centre for further processing.

Written By:

Kristina is the Sr. Director of Marketing Communications at ShipBob, where she writes various articles, case studies, and other resources to help ecommerce brands grow their business.

Read all posts written by Kristina Lopienski