Show System Volume Level in Conky

Showing the current (system) volume level from Conky is not generally available via a variable; however, it is possible with execpi and a system call such as:

Via amixer (alsamixer)

Vol: ${exec amixer -c 0 get Master | grep Mono: | cut -d " " -f6}

amixer is generally available in most linux distros by default and provides a quick, simple volume level. Credit goes to a answer

Via pactl (pulseaudio)

Vol: ${execpi 500 pactl list sinks | grep "Volume: 0" | cut -d " " -f4 }

If you use pulseaudio, pactl can be used as above.

Other Methods

The logic will be the same if you use other sound libraries, simply change to the api for your desired library and feel free to post a comment so I can add for others.