Pulling Strings - Understanding Scale Length and String Tension

Back in 2018 (I think) I encountered my largest shift in customer string requests ever in my career as a luthier. It seemed like everyone was trying out odd string sets - 9.5’s, 10.5’s, etc. The half guage sets were new to me, but our major supplier (D’Addario) seemed to have a set for everyone - and if they didn’t String Joy came to the rescue!

I found out soon after that Rick Beato had made a very interesting video post regarding using lighter strings instead of heavier strings for “better tone”. While “better” is subjective to say the least, there is a valid reason that changing string gauges might be a good option for you to explore.

Scale Length. Maybe it’s a little unclear to you as to what scale length is. Scale length is best described as the complete length of the strings from nut to bridge. Typically we can find an instrument’s scale length by measuring the distance between the nut and the top of the 12th fret and then simply multiplying the measurement by 2. Typical scale length for Fender guitars is 25.5” while Gibson is 24.75”. Paul Reed Smith revolutionized (debatable for sure) the game by building guitars with 25” scale length, and in modern times multi-scale instruments have taken the crown by shifting to hybrid scales (such as 28” on the bass side and 25” on the treble side).

But what gives? Why are there different scale lengths? That’s a tricky question to answer in entirety, but partially we owe the answer to personal preference. Everyone experiences playing guitar differently. Some players fight the guitar with a passion, while others finesse the guitar with compassion. There is no one solution to what feels right for everyone. So in a bid to achieve success in each area of the market, manufacturers choose their paths and offer what they can to appease all types of players.

Tension. Well, here comes physics. Brace yourself for some headaches. Unless you play a traditional Indian Sitar, your frets are in a fixed place and your scale length is already determined. The strings you choose for your instrument and your desired tuning have a direct relationship with each other.

To quote another souce: “The basic rule of scale length is simple: For any given tuning and set of strings, longer scales have higher tension. Once again, it's important to note that this only applies to the area of string that is vibrating between the nut and saddle.”

Let’s use the big 3 as a frame of reference.

Fender guitars are 25.5” scale length, Gibson guitars are 24.75”, and Paul Reed Smith guitars are 25” (please note that these are general terms since each brand does have deviations in their scale lengths per model).

So let’s look at those numbers like this:

25.5

25

24.75

Ok, so we have scale length. Now lets assume we have each guitar and each are in standard E tuning. If you put a set of 10-46 strings on each guitar, the tension would feel different with each scale length. The 24.75” guitar would feel loose, the 25.5” guitar would feel tight/taught, while the 25” guitar would go either way (ala Goldilocks). Well, I’m not trying to say that PRS “nailed it”, but there is some evidence here that finding a middle ground between accepted ranges might be a pathway to success. Still, the science is now proving that tension across different scale lengths with different gauges does feel different.

So what happens when you drop tunings? This get REALLY complicated. No two strings companies adhere to the same core to wrap ratios. The biggest factor to consider is the core of the string being used when determining tension. A 46 low E from one company might measure “46” with a caliper, but the tension might be high or low depending on the core size. A wound string consists of a solid core (unwound G through E for reference) wrapped in a smaller wire to increase mass and diameter (the diameter is what we refer to with the size). If the core measures 24, then the wrap is no more than 22 for a 46, while a core of 20 has a wrap of 26 for the same gauge. So these two examples will have vastly different tensions at normal tuning!

So, your first mission is to choose a brand that caters to tensions and NOT gauges. Ernie Ball has marketed this feature for years by calling their offerings as a scale of “Slinky”. D’Addario is less than favorable in the reception of tension but offers an impressive array of sets per tuning preference. Dunlop is another offering that makes tension a key feature by offering “heavy core” strings.

What Is RIght? Well, that depends. Any tech or luthier will give you their own preference per situation, but here’s our take on the matter…

Let’s go with 25” as “the standard” for normal tension.

25.5”: use 9-42

25”: use 9-46

24.75: use 10-46

Using D’Addario string sets for consistency, this formula seems to work at standard tunigns for a baseline. Now, what would happen if you dropped tunings a half step (Eb standard) and wanted the tensions to remain basically the same?

25.5”: use 10-46

25”: use 10-52

24.75”: use 11-49

Right off the bat you might question: “What’s with the jump to 52 on the E with 25” scale? Well we need to go back to the “core vs wrap” situation. With D’Addario the tension of a standard wound 52 is different than a 52 from Ernie Ball or Dunlop, so dropping tuning a half step and compensating up to a wrap measurement of 52 will not mean a core tension has been drastically increased.

Yup. We lost you. And honestly we have lost ourselves too.

There is way too much science behind choosing string gauges per tuning per guitar than can be laid out in one blog post. In general, you have to establish a baseline for yourself. This involves an evaluation of what instruments you have and what their measurements are. Depending on the results of those measurements we can then determine was string gauge might work for your tuning and playing style. Then with little bit of experimentation we can determine your personal baseline and deviate from there per instrument and tuning combined. As an example, my personal preference today for 25.5” scale length is 10-52 (D’Addario). Since I play some odd instruments, I have everything from 10-52 to 11-56, and even a 13-68 set on a baritone model in C# standard. So you can see how this can get confusing and slightly skewed based on a large amount of factors.

Don’t let anyone tell you that you “need” to drop or increase string gauges because they “Use it and it sound better”. Better for them is not better for you. The solution is in talking to an informed tech who knows the tension sciences and can apply them to you and your needs.

The only time we should all reduce tension in a general sense is emotionally. However when it comes to guitars, sometimes we need the fight to feel at ease.