How many strings does a standard acoustic or electric guitar have?

How to get close to this number

Reason from the hand. A fretting hand has four usable fingers and a thumb, and a string count has to be playable as a chord in one grip — six is what a hand can span and barre comfortably. Instrument design is constrained by anatomy more than by acoustics, and this is the clearest case.

The tuning is the part worth knowing beyond the count. The intervals are mostly fourths with one third in the middle, which is a deliberate compromise: consistent fourths would make scales simpler but chords harder to reach, so the standard tuning trades theoretical tidiness for playable chord shapes.

The twelve-string variant in the explanation does not contradict the count; it doubles it. Each of the six courses gains a second string tuned in unison or an octave up, producing a chorus effect from a single strum. The instrument still has six pitches — it has twelve strings producing them, which is why the courses rather than the strings are the real unit.