The fretboard below show the notes for a 4-string Guitar when "Plectrum Guitar" is used. The strings are tuned to the following notes:
C3G3B3D4
For other alternatives see the available tunings for 4-string Guitar
The tuner is fully chromatic but if you need a reference of a specific tuning when tuning by ear or if you want to tune any other instrument follow the steps in how to setup the guitar tuner for other instruments