It is my understanding that strings, over time, stretch and are unable to maintain their tension, so they go out of tune at a lower pitch.

When I pick up my guitar and I tune it with my electronic tuner, I often find most strings at a higher pitch than they should be... this means that they have gained tension... how is this possible?

This has happened to me with two different guitars in two different houses and over a sizeable period of time (months), so I'm starting to suspect that I'm doing something wrong.

  • Good question. I have a guitar that has one string go up. Although, I always assumed that the rest of the guitar had gone flat. I've never even thought to check it with a tuner.
    – yossarian
    Feb 8, 2011 at 23:52
  • Does your guitar have a tremolo? Do you leave the tremolo bar on the guitar when it's in its case? Do you put anything over the neck or body in the case that could cause pressure against the guitar/neck when the lid is closed? Do the cases fit the guitar correctly? The guitar shouldn't shift or rattle around when the case is closed, nor should you have to force the lid closed. It should be a firm fit all the way around.
    – Anonymous
    Feb 9, 2011 at 3:00
  • @the Tin Man: this has happened to me with two different guitars, one with the whammy bar and one without. But, in both cases I tend to not put them in a case, but leave them on their support.
    – UncleZeiv
    Feb 10, 2011 at 23:12
  • I have the same problem with a Charvel that looks like this : pepechuy.com/amwg/guitars/charvel/1CharvelGuitars-BlkM3A/… . A friend of mine changed its bridge and put a floyd-rose instead. I didn't know that was wrong, I still don't understand why it is wrong, but everybody says that the problem is with the floyd-rose. May help.
    – jeff
    Apr 11, 2015 at 15:37

8 Answers 8


Your strings have gained tension due to the change in temperature and humidity causing the wood of your guitar to expand and contract. Metal strings don't expand or contract enough to cause detectable tuning issues alone. The wood of your guitar, however, does. The truss rod does the best job it can for keeping your neck at the right angle relative to the body, but it's not perfect. A slight movement of the neck backwards (towards the z axis relative to the body of the guitar) will cause your strings to go sharp enough for your ear to discern. You can test further this by playing open strings and pushing on the headstock in different directions perpendicular to the body of the guitar--just don't push too hard. As relative humidity changes, the wood of the body and neck of a guitar will expand and contract in two ways: tangentially and radially. Tangential movement lies parallel to the growth rings of the wood while radial movement is perpendicular across the growth rings. Another thing to consider is that different species of wood are more hygroscopic than others. This simply means that one species, take Maple with a radial growth coefficient of 0.00353 for example, will absorb more water--and thus move more--than another species like Cherry that has a lower radial growth coefficient of 0.00248. So, while the neck of your guitar gains or looses moisture, the wood will expand and contract relative to one of the two directions I explained earlier. This movement in either direction can very well be enough to cause more tension on the strings, thus bending them sharp.

A great article explaining all this a little more lives here. It's about cabinets, but very much applies to anything made of wood because the physical properties are universal.

Also, another list of some common woods and their growth dimension coefficients is here. According to that book mahogany is on the lower end of the spectrum, so it doesn't move very much. However maple, a very popular wood for guitar necks, tends to move a lot tangentially (parallel to the growth rings, or grain of the wood) and consequently is a little more susceptible to changes in humidity.

So there's the physics of it :D. In the end, the environment your instrument lives in is very much an factor to it's overall health--especially if it's made of real wood.

Also, see the answers on this question for other ideas as to why your guitar goes out of tune (usually).

  • Thanks for the very thorough answer. It makes a lot of sense. I should have mentioned that this has happened to me both at my old place and at my current place, and I've had humidity issues in both of them. Plus, I'm a novice and I've got an entry level guitar, so I guess it's even more sensitive to the environment.
    – UncleZeiv
    Feb 10, 2011 at 23:15
  • While it's true that metal strings don't react noticeably to humidity changes, they do indeed react to temperature changes: temp up, strings down, and vice versa. May 31, 2017 at 17:35

This happens to me quite a lot, and I have put it down to the fact that I play my guitar in a number of different rooms in my house. The reason that this would have any effect is the room temperature.

If the guitar's surrounding atmosphere changes by even a couple of degrees, things can change. The metal strings expand or contract, depending on which direction the temperature is shifting. If the temperature gets cooler, the strings contract, which causes more tension, and vice versa. Changes in moisture and humidity can also cause differences, as the wood can change depending on humidity levels. Do you set your heating to go off at night or during the day? There could be many other reasons.

As with most tuning related problems, in my own personal experience the G and B strings are usually the worst culprits in this situation.

Hope this helps.

  • 2
    When the humidity goes down (I live in Houston, so it can go down alot) all of my strings will be sharp. Feb 9, 2011 at 1:04
  • That makes complete sense. Lower humidity causes the wood of your guitar to shrink. Wood tends to shrink perpendicular to the grain, and necks are almost always cut with the grain running parallel to the fingerboard. Therefore, as the wood shrinks it will move backwards toward the body of the guitar.
    – Jduv
    Feb 9, 2011 at 1:31
  • 1
    The strings actually don't expand and contract enough to cause detectable tuning issues as related to environment. They will expand and contract during usage due to forces exerted on them.
    – Jduv
    Feb 9, 2011 at 1:33
  • Alistair's answer is great that's for sure :). I'm still verifying the "strings don't stretch enough to make a difference" claim that I made, and if I find something wrong with it I'll change (and give credit where it's due).
    – Jduv
    Feb 11, 2011 at 2:21
  • Damnit - I live in the UK. Humidity doesn't go down :-)
    – Doktor Mayhem
    Feb 22, 2011 at 15:17

I find the strings ALWAYS higher, never lower, dilatation due to variation of humidity should work both ways, not always higher. The only guess I can make is that when I augment the tension of the string, because of friction on the bridge, some tension remain accumulated in the part of the string between the tuning peg and the bridge, and then that tension gradually relases increasing the overall tension of the string.

  • (Being a beginner totally dumb when it comes tuning I always release the string a lot and tune increasing tension, so my case may be specific to this way of tuning)
    – user23208
    May 19, 2016 at 12:42
  • A little nut grease lubrication can go a long way to insure the strings don't bind in the string slots of the nut. Jul 22, 2018 at 14:37

On top of reasons such as humidity and temperature, It can also depend on how your strings are wound. Unwound strings in particular can slip if they're not wound correctly, these are the B and high E strings on most acoustic guitars. (For more information on how to wind strings, have a look at this question: How to wind strings on the tuning posts.)

  • 1
    Although such slip would make it lower rather than higher
    – jclozano
    Jan 2, 2012 at 21:11

While your strings' tension may be impacted by the expansion or the contraction of your guitar wood. (As explained by Jduv). Steel or Nylon strings expand and contract more than wood. According to [engineeringtoolbox][1], steel's thermal expansion coefficient is around 4 times as wood's (parallel to grain or perpendicular to growth rings). My theory is that when you're playing your guitar, the strings get warmer due to all the friction and heat transferred from your fingers. So when you leave your guitar perfectly tuned, the almost inevitable drop in temperature of the strings will cause them to shrink much more than wood, making them increase in tension and go sharp.

I'm considering wood's radial expansion and not the tangential because I think the latter has little effect on the strings. In fact, if the wood in both the neck and body expands or contracts perpendicular to the strings with the same amount, that will just shift them up or down respectively without impacting their tension. There might be however a difference between the body's expansion and the neck's, especially if they're not made out of the same type of wood. But this difference doesn't account for the strings' effect. In fact you'd need a pretty big perpendicular bend to account for the same parallel shift. This can be proven mathematically after making a few assumptions, but you can also test it yourself: Shorten or loosen a string by 1mm and then bend the neck by 1mm and see which shifts the frequency more.

Of course, this is only a theory which tries to simplify a pretty complex phenomenon where many factors come in to play and which needs experimental data to either back it up or discard it.



If your guitar has a tremolo bar, it may also be caused by the springs that lose their tension (on a floyd rose type of tremolo, I don't know how the other systems work, but I guess it is also based on springs).

But I would go with the temperature or humidity change.


Guitars and tuning problems. At one time I tightened every loose screw I could find on my tuning pegs, snugged them up pretty good thinking it would improve something. Big mistake. Researched and found most tuners work best with a little play in them allowing them to "lean in" ever so slightly. I loosened the screws just a touch, and my tuning issues disappeared, I also use nut grease to aid in the movement of the strings in the string slots and eliminate binding there. I hope my experience can help others avoid some tuning issues.


I have the same thing happen on fender acoustic and squire start electric. It could happen very quickly after just a few hours; being a finish carpenter I know that the wood is not going to pull in or lose that much humidity that quickly. So I would venture to guess it's our technique coupled maybe with the styles we play. I've been using finger picking for classical and jazz, I've always tried my best to have a sound like Wes Montgomery who actually just used his double jointed thumb to achieve his sound.

  • I don't see a way that playing style could cause this, unless that style involves turning the tuning pegs. I frequently play just finger picking and my strings detune normally (they get lower).
    – user28
    Apr 23, 2016 at 23:42

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