✓ Royal Mail Authorised Inspector since 2008 | Trading since 2005
Royal Mail defines an International Letter by its size and weight. To qualify for the International Letter price, your item must be no larger than 240mm x 165mm, no thicker than 5mm, and weigh no more than 100g. Anything larger, thicker or heavier must be sent as an International Parcel.
How Royal Mail Defines an International Letter
Royal Mail has made it easier to work out whether your mail qualifies for the International Letter price. The classification is based simply on the weight and dimensions of the letter, so you can check an item quickly before you send it.
International Letter Requirements
To comply with the Royal Mail requirements for the International Letter price, letters must be:
- No larger than 240mm x 165mm
- No thicker than 5mm
- Weigh no more than 100g
If your letter is either larger or thicker than the requirements above, then you must class the item as an International Parcel instead and apply the correct postage cost.
Reducing the Cost of Larger International Items
If you would like to reduce the overall cost of sending a larger international item, you can fold your mail to fit into a C5 envelope where this is possible for your letter. This will allow you to pay the lower International Letter price, but the thickness of the letter must not exceed 5mm.
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FAQs
What are the maximum dimensions for a Royal Mail International Letter? To qualify for the International Letter price, an item must be no larger than 240mm x 165mm, no thicker than 5mm and weigh no more than 100g.
What happens if my international item is larger or thicker than the limits? If your item exceeds the size, thickness or weight limits, it must be classed and posted as an International Parcel with the correct postage applied.
Can I fold a larger item to pay the International Letter price? Yes. If possible, you can fold your mail to fit a C5 envelope and pay the lower International Letter price, provided the thickness still does not exceed 5mm.

