C5 - What is C5?

Definition of C5:

An international standard for paper size, most commonly used for envelopes. The C5 size is defined as measuring 162mm wide by 229mm high (with a tolerance of +/- 2mm). A sheet of A5 will fit into a C5 envelope.

Here is the Harvard-style citation to use if you would like to reference this definition of the word C5:
Label Planet (2020) What is C5? | C5 Definition. Available at: https://www.labelplanet.co.uk/glossary/c5/ (Accessed: January 1, 2023).