IOS supports sixteen privilege levels(0-15), but by default all the commands are grouped into level 0(zero), 1(user) or 15(enable). For example level 0 has commands like enable, disable, exit, logout and help. Level 1 has lot more commands and level 15 allows all the possible commands. Is there a way to check which command requires which privilege level?

In addition, one could change the privilege level of the command. For example modify the privilege level needed for "show startup-config"

privilege level exec level 8 show startup-config
How should one know that in this particular device privilege level 8 is needed for "show startup-config"? Is there a way to check which privilege level is needed for a particular command?