Along with "what overdrive pedal are you using", "why are you playing so many notes?" and "why are your jeans so ripped?" (I see you, YouTube user jm0pq76q), perhaps the most common guitar playing question I'm asked is "what gauge of strings are you using?". I'm a serial string-gauge experimenter: I played 9s growing up, but I've had spells playing everything from 8s to 12s.
Let's first start out by addressing the elephant in the room: string gauge matters, but not for the reasons you might think. There's a common bias that bigger strings sound "better", and light strings are for effete weaklings that lack the manly man strength to play manly man strings and thus will forever be barred entry to the exclusive "big strings big tone club". As well as being exclusionary, this belief is pure nonsense. I've seen 12-year-olds playing 12s, and competitive powerlifters playing 9s.
String gauge is a very individual thing, and it's important to get the right size of string to match your playing style. While SRV had a phenomenal tone playing big strings, you can't extrapolate that to mean that YOUR tone will be better with big strings. To put it another way, Usain Bolt wears a UK size 13 shoe, but if I bought some size 13s, it's highly unlikely that they'd make my 100m time faster.
So let's put bias aside for a moment and talk about what DOES matter and how you should select your strings.
PLAYING STYLE:
The most obvious consideration when choosing a string gauge is your playing style. If you spend most of your time smashing out big riffs and chords, the added stability of a thicker gauge might be ideal for helping you stay in tune, especially if your attack is heavy. By contrast, if you're a bit of a shred-head with a lighter touch, a lighter gauge will help you keep your bending and vibrato feeling effortless and stop tension creeping into your playing.
FRETTING PRESSURE:
This is where individual differences in hand strength really come into play. Some players, even with a very relaxed touch, just can't keep light strings in tune. If you have tall frets, this can be even more of an issue. If you have this problem, the first course of action is to assess your technique and make sure you're not power gripping, but if you're keeping a relaxed touch on the guitar and still having tuning problems, maybe try a gauge up.
The opposite is true if you have to exert excessive force just to fret notes. Fretting should feel like it's no effort at all, and if you have to really squeeze hard just to get the notes out, consider moving down a gauge.
YOUR INSTRUMENT:
Lastly, there's your instrument itself! Do you usually go for 9s on your Tele, but you've recently bought a Les Paul and want the same feel? Maybe try 10s. As a rule, a given string gauge on a shorter scale length guitar (like a 24.75" Les Paul) will feel looser than they would one a longer scale length guitar (like a 25.5" Fender scale guitar).
Another consideration is tuning. As a rule of thumb, for every tone (two frets) that you tune down, you should go up one full gauge to maintain a similar playing feel. If you're used to 10s in standard, but would like to experiment with drop C (low to high: C-G-C-F-A-D), maybe try 11s, with the lowest string from a set of 12s if you really want to maintain the same tension across the set.
One final consideration is any quirks the instrument may have. If you have a vintage instrument that you just can't get the action low enough on for a slinky feel, a lighter string gauge might offset that somewhat. Likewise, if you have a tremolo-equipped guitar, a lighter gauge will enable you to set the trem up so it's more sensitive, while a heavier gauge will require more spring tension resulting in a stiffer feel (which might be exactly what you're looking for!).
So there you have it: some things to take into consideration when it comes to finding the right string gauge for your personal style.
Remember, there is no "better" or "worse" when it comes to string gauge (no matter what the "blues bro" down the local guitar shop told you), so don't be afraid to experiment. Strings are pretty inexpensive, too, so try a bunch of sets and find what works for you. You won't be sorry.
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