How this conversion works
FF is hex for the maximum byte value. Reading it out: F is 15, so FF is 15x16 + 15 = 255. You meet it constantly as the fully-on channel in a colour like #FF0000.
Each base just uses a different set of digits for the same quantity. Reading
ff as a hexadecimal number gives the decimal value
255; expressing that same value in base two, eight or sixteen
produces the rows above. To convert any number between bases — including custom bases from 2
to 36 — use the number base converter.