Sometimes when you put a new set of guitar strings on an acoustic guitar it won’t play perfectly in tune. It can be necessary to use a different gauge guitar string. For example, if a 24-gauge guitar string will not play perfectly in tune you might need to change to a 23-gauge guitar string or possibly a 25-gauge. Different thicknesses of strings will increase in pitch at different tensions, a small change in guitar strings can compensate for minor pitch discrepancies. Electric guitars have an individual saddle for each guitar string that is adjustable. This allows you to calibrate your electric guitar. You do not have that option on an acoustic guitar.