Many questions that often comes up on the boards are those involving string gauge. This thread will help to create a knowledge base of sorts to help guitarists with their string gauge woes. To aid me in creating this, I have chosen to use this string tension calculator: String Guage and Tension Calculator - Version 0.1.4 - 26 apr 1998. It's not 110% accurate but it's accurate enough to positively answer MANY, if not most questions involving gauge, scale, etc. Let's start with some basics involving the factors at play. Scale Length This is the estimated distance from the string's two termination points. One being at the nut, the other being at the bridge. What does that measurement have to do with string gauge? Well, look at it like this: say you take a rubber band and stretch it 12" and feel the tension that the rubber band is exerting. Now, stretch that same rubber band to about 18", now feel the tension. You should be able to easily tell a difference in tension. Now, in order to sound a given note, a string of a certain gauge must be under a certain amount of tension. The tighter, the higher the pitch. The looser, the lower the pitch. Tension Here, we'll be looking at tension as a measurement in lbs. Thus, for instance, if the scale of the guitar is 25.5" and a .009 gauge string is tuned to a standard 6-string guitar's high E (E4), the tension would be 13.13lbs. If we reduced that tension to 10.42lbs, then the note would ring out as a D, or one step down (D4). Gauge The gauge of the string, is it's thickness, or the diameter of the string itself. For instance, the commonly referred to "9s", are .009", or nine one-thousandths of an inch. The thicker the string, the more tension it'll need in order to reach a higher pitch. For instance, where a .009 at E4 is at 13.13lbs of tension, a .010 (just 1/1000 bigger) would have a tension rating of 16.21lbs at E4 on 25.5" scale. Why is tension so important? Well, to best illustrate this, lets perform an experiment. Take your guitar and down tune the low E (6th string, E2) and tune it down to B (B1). Notice how loose the string is, and how it buzzes and overall, just doesn't sound so great? That's why having proper tension is so important. It's why all the strings on your guitar aren't the same exact size, but a calculated, ever increasing gauge as the tuning of the strings gets lower. If we can just keep using bigger strings, why bother with longer scales? The lower you tune, the thicker the string will need to be to still have that ideal tension (which is different for everyone), eventually the string will have to be so wide around, that it's feel and timbre (tone) will start to suffer. So why hunt down the proper strings? To give your self the ideal feel, tension, and timbre on your chosen instrument taking scale and tuning into consideration. Look at it as finding the right sauce to put on your pasta.