Royal Mail classes anything under 100g and 240mm x 165mm x 5mm as a Letter, while anything above this and under
750g and 353mm x 250mm x 25mm is a Large Letter. As you might expect, Large Letters are subject to higher fees,
so you should use smaller envelopes wherever possible. You can find the envelopes and their sizes categorised
according to the Royal Mail pricing system in the table below. Remember that you must also take into account the
thickness when posting:
Royal Mail category |
Envelope |
Size |
letter |
DL |
220mm x 110mm |
C10 |
40mm x 28mm |
C9 |
57mm x 40mm |
C8 |
81mm x 57mm |
C7 |
114mm x 81mm |
C6 |
162mm x 114mm |
C5 |
229mm x 162mm |
Large Letter |
C4 |
324mm x 229mm |
You can purchase books of First and Second-Class stamps for Letters or Large Letters here at Viking - perfect if
you want to avoid queuing up at the Post Office.
The current Royal Mail pricing is based on the weight and size of an item being mailed, so you don't have to pay
more than you need to.