When you’re sending parcels via Royal Mail, getting the size right is essential. Whether you’re posting gifts to loved ones, selling products online, or managing business logistics, understanding Royal Mail’s parcel size categories helps ensure your item is delivered without delays. And avoids unexpected fees.

In this guide, we break down Royal Mail’s parcel size categories, including measurements, weight limits, and pricing implications.

The 4 Main Royal Mail Parcel Size Categories

Royal Mail divides parcels into four main size brackets:

1. Letter

• Max Size: 24cm (L) x 16.5cm (W) x 0.5cm (D)
• Max Weight: 100g
• Perfect For: Flat documents, greetings cards, certificates

Letters must be flat and lightweight. If your item is too thick, it moves into the next category.

2. Large Letter

• Max Size: 35.3cm x 25cm x 2.5cm
• Max Weight: 750g
• Perfect For: Books, notebooks, slim product packaging

This is ideal for slightly bulkier but still flat items. Anything thicker than 2.5cm will be classed as a Small Parcel.

3. Small Parcel
   

• Max Size (Box Shape): 45cm x 35cm x 16cm
• Max Weight: 2kg
• Perfect For: Clothing, small electronics, boxed items

This is one of the most commonly used sizes for e-commerce sellers and general posting.

4. Medium Parcel

• Max Size (Box Shape): 61cm x 46cm x 46cm
• Max Weight: 20kg
• Perfect For: Bulkier items, kitchen appliances, multiple products

Once your item goes beyond these limits, it becomes a Large Parcel, which Royal Mail only handles via Parcelforce Worldwide.

At-A-Glance Comparison

Using the right size for minimal impact

Using right-sized packaging isn’t just good for postage, it reduces excess void fill and cuts carbon emissions during transit. All our used boxes as well as our mailing bags are measured and sorted so you can easily match them to Royal Mail categories to ensure you save money and keep your impact to a minimum.

Pro Tips for Packing Within Size Limits

• Measure once packed: Dimensions include the packaging.
• Choose your box before you pick your shipping method.
• Use soft void fill (like shredded kraft or honeycomb paper) to stay within size and protect contents.

Understanding Royal Mail’s parcel size guide is crucial for avoiding extra charges and ensuring timely delivery. Always double-check the size and weight of your parcel before posting, and when in doubt, visit your local Post Office for advice.

Need eco packaging that fits Royal Mail size guidelines?

Shop used small parcel boxes, medium parcel boxes and mailing bags.