PMR446 is a license free radio frequency band for use in Europe. It was introduced in 1998 and to this day remains one of the most popular license-free general purpose radio bands here in Britian.
The letters in PMR446 mean PMR (Personal Mobile Radio) and the numbers relate to the frequency of usage (446 mHz).
PMR446 exists in the UHF radio spectrum and consists of sixteen FM 12.5 khz channels. Each channel is seperated by 12.5 khz spacing. Originally there were eight channels however in 2015 it was extended.
Below is the frequency chart of the PMR446 channels:

Channel number | Channel Frequency | Notes |
1 | 446.00625 mHz | Default channel on most brands of radio |
2 | 446.01875 mHz | |
3 | 446.03125 mHz | |
4 | 446.04375 mHz | |
5 | 446.05625 mHz | |
6 | 446.06875 mHz | |
7 | 446.08125 mHz | |
8 | 446.09375 mHz | Calling Channel |
9 | 446.10625 mHz | |
10 | 446.11875 mHz | |
11 | 446.13125 mHz | |
12 | 446.14375 mHz | |
13 | 446.15625 mHz | |
14 | 446.16875 mHz | |
15 | 446.18125 mHz | |
16 | 446.19375 mHz |