How high should classical guitar action be?
What is the correct action for a classical guitar? There seems to be an unofficial standard evolving on this. Action is measured as the distance between the frets and the strings. Specifically, the distance is measured at the 12th fret from its top to the bottom of a given string.
An action of 3mm at the first string (top E) between the string’s bottom and the top of the 12th fret is considered normal. And an action of 4mm at the sixth string (bottom E) is considered normal – with the strings in between having values between 3 mm and 4 mm progressively.
These figures may vary up or down slightly but no more than 0.5mm. A difference of 1 mm is generally considered advisable between the bass and trebles.
Some experts suggest taking another set of similar measurements at the first fret. The action numbers here will be really low: 0.8mm from bottom of 6th (low E) string to the first fret and 0.6mm from 1st (high E) to fret would be considered ‘normal’.
Older guitars – often from famous luthiers – have their 12th fret action numbers usually exceeding the above ‘normal’. Even many concert performers today prefer action numbers that overrun the ones above.
The “best” action will thus be different depending on the player and a few other variables we will shortly see. So let’s get this straight. Even if the numbers exceed the ones given above, for some players, there still may not be a problem at all.
As a related issue, there is such a thing as having too low an action too. Which in turn causes a different set of problems including string buzz. If you have the 3rd string buzzing, then check out my article How To Get Rid of G String Buzzes for helpful tips. | 
