Royal mail dimensions for large letter

According to Royal Mail's guidelines, a Large Letter is defined as a letter that measures more than 76mm (3 inches) in thickness, but not exceeding 91mm (3.6 inches) in thickness.

Here are the maximum dimensions for a Large Letter:

Please note that these dimensions are subject to change, so it's always best to check with Royal Mail's website or consult their latest postal guides for the most up-to-date information.

Additionally, it's worth noting that Large Letters are subject to a higher postage rate compared to standard letters, and may also have specific packaging and labeling requirements.