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If you’ve ever seen a guitar string snap (or, worse yet, been hit by one as it snaps — ouch!), you know that there is a lot of tension stored in a string.
Maybe that led you to wonder: How much pressure do guitar strings put on the neck of a guitar?
The amount of pressure, or tension, a set of guitar strings puts on the neck will vary with string gauge and tuning, but for a guitar in Standard Tuning — E A D G B E — it’s likely between 65 pounds and 200 pounds and more than 250 pounds for a bass.
If that seems like a lot, it is, but don’t worry — almost all guitars made within the last 50 years can take a lot more pressure than that.
So what all goes into string tension, and how do guitar makers cope with the pressure (literally!)? Let’s take a look.
How Do You Know What The Right String Tension Is?
The question of string tension doesn’t have a single answer, but figuring out the answer for a particular guitar isn’t hard.
Every string has to be tuned to a certain tension to play a given pitch (remember pitch is not the same thing as tone). That tension will change based on what the string is made of and its thickness, or gauge.
That might have left you wondering: what tension do my strings put on the neck when tuned up? There are a few ways to check.
Many manufacturers, but by no means all, publish a list that shows the proper tension for a string at a given pitch. String makers from Curt Mangan to Elixir to D’Addario offer charts showing the tension based on string type and gauge.
If you don’t have one of those brands and don’t know the manufacturer’s tension, you can use gauge to estimate. The site String Tension Calculator uses the tension from Kalium Strings as a baseline and lets you choose each string’s gauge, giving you the tension.
Looking at the Curt Mangan chart shows how much variation there can be in string tension. The thinnest gauge high E string, a .008″ string, has a tension of 9.8 pounds when tuned. The thickest, a heavy gauge 0.14″ string, has a tension of 29.92.
How Much String Tension Is On A Guitar Neck?
Once we know the tensions, the rest is nothing more than addition. You take the force that each string exerts and add it to the next.
For the lightest possible and heaviest possible set of strings listed in the Mangan chart, that gives us this.
Adding up the tensions, the lightest gauge string set gives a total pressure on the neck of about 66 pounds for a 24.75 inch scale guitar and 67 pounds for a 25.5 inch scale guitar, while the heaviest gauge string set gives a total pressure of about 178 pounds for a 24.75 inch scale guitar and about 182 pounds for a 25.5 inch scale guitar.
How Much String Tension Is On A Bass Guitar Neck?
As you can see pretty clearly from the numbers above, the amount of tension needed to tune a string to a certain pitch goes up with the the thickness of the string. That effect is magnified by scale, or the length of the string that actually vibrates to create the sound.
Take a theoretical set of medium to heavy gauge bass strings, which are for a 34 inch scale bass.
The neck of a bass with this set of strings would be under about 260 pounds of tension. If strung with light gauge strings, a bass could have tension on the neck closer to 150 or 175 pounds, similar to a guitar.
A six string bass strung with heavy gauge strings, though, would have a massive amount of string tension, likely more than 300 pounds.
How Do Guitar Necks Resist Bending Under String Tension?
Numbers like the ones above might make you wonder whether guitar necks are likely to snap — imagine holding 260 pounds of pressure!
But, of course, wood is usually quite strong, and guitar necks are strung to make use of that strength. Rather than breaking, what a guitar neck does is bend.
Some bending is OK — that flexibility is what makes wood such a great choice for instruments, because it can transmit vibrations. And even in older guitars that used lower tension strings, guitar makers built necks to be as strong and resistant to bending as possible.
Too much bending is definitely not OK, though, and could be anywhere from a mild inconvenience to a major catastrophe, depending on the kind of guitar and how valuable it is.
The way guitar makers have helped to deal with the problem of string tension for a century is the truss rod. While reinforcing rods probably appeared before them, some Gibson engineers patented an adjustable truss rod in the 1920s.
How Do Truss Rods Help With String Tension?
Wood under tension from strings has a tendency to bow.
If that bow gets too great, the strings are pushed high above the fretboard, making a guitar hard to play and giving it intonation problems.
If a bow that was too much were left alone and the string tension were left on the neck, it could essentially ruin the guitar, making it both unplayable and difficult to fix without completely replacing the neck.
In its most basic form, a truss rod is a piece of metal that is anchored in the neck of a guitar. Tension on the rod counteracts the tension from the strings.
A nut at either the top or bottom of the neck lets you adjust the truss rod, which is one way to change the action of a guitar.
This video explains how to adjust a truss rod. It’s by a physics teacher and he gives a breakdown of how the truss rod works:
How Much String Tension Is Too Much?
With a steel rod for support, even huge amounts of tension aren’t much trouble for the neck. That doesn’t mean too much string tension can’t cause damage, however.
If left with too much tension and the wrong neck relief from an improperly adjusted truss rod, the wood below a guitar’s bridge can start to raise — called bellying — something only a qualified guitar technician could fix.
You also risk a sudden failure if you put too much tension on a string, and that could hurt quite a bit if you’re hit by the string as it breaks and this is more likely to happen the older the string is.
With tuned up strings there is a lot of tension on a guitar’s neck and bridge, but generally not more than any modern guitar can handle.
Makers do a lot, from adjusting the bracing and makeup of an acoustic guitar’s top to putting truss rods and now even carbon fiber reinforcement rods into necks, to keep the string tension in check and your guitar in playable condition.
I’ve been a musician, particularly a guitarist, for more than 25 years. I love writing about guitars, gear, recording, music in general and more.