What is the correct action for a classical guitar? Learn here how to measure it easily.

Video Transcription Text:

This measure is something basic that every classical guitarist should know. Not only classical but all kinds of guitarists. Maybe you already know it but my experience tells me that there are a lot of guitarists who don’t know it or don’t know how important it is. And some of those who do know it often don’t take it correctly.

I’m talking about what is called the string height at the 12th fret. That is; the distance from the 12th fret of the guitar to the bottom of the string.

This measurement is taken on both the sixth and first strings to measure and determine the action of your guitar.

If these measurements on your guitar, either one or the other or both at the same time, are not correct then we are probably talking about a guitar that is difficult or very difficult to play and therefore will need to have this problem fixed.

And be careful if the height is too high we are talking about a playability problem.
But also if the height is too low we are talking about other possible problems like buzzing noises or loss of sound projection of the guitar.

-How to Measure it-

Let’s explain it in detail.

I’m going to explain to you an easy way many guitarists and guitar makers use it.

In these pictures, you can see what measurement you should take. Remember that it is taken correctly from the top of the fret to just the bottom of the string. Some people take to the middle of the string but that is not correct. I repeat the correct one is from the top of the fret to the bottom of the string

Here we see it with the sixth string.

Here we see it with the first string.

How do we measure it?

Well, it’s easy with a precision ruler. That is with a ruler that is divided if possible not only in millimetres but also in Half millimetres. And very important, the first millimetre of the ruler must coincide with the edge of the ruler. Don’t buy a ruler that has a blank space between the edge of the ruler and the first millimetre, because it won’t work, it will be useless for our purpose.

Another important thing before measuring. If you have removed the tension of the strings of your guitar for whatever reason then put it on again and leave them taut for a few hours in the correct tension the strings must be for a normal guitar tuning.

Why do I tell you to put tension on the strings?

Because the neck of the guitar with the tension of the strings gives in angle a little bit and leans a little bit towards the bridge. And therefore, the measurement that we are measuring, which is the height from the fret to the string, is probably going to increase a little bit.

Once we have the right ruler and the guitar strings under the right tension, then we can start to measure.

As you can see, I place the ruler behind the string, where the millimetres on the ruler are marked.
Be careful of two things, firstly do not move the string when measuring with the ruler as this can change the height. And second, make sure that the ruler is completely straight at a 90-degree angle with the fret. In this way, we can see that for example, this guitar has 2.8mm of height on the first string. And we do the same with the sixth string and this guitar there has 3.8 mm.

In other words, this guitar has what I and many others consider to be a standard string height measurement for a classical guitar…

Does this mean that your guitar has to have this exact measurement to be comfortable?

No, it doesn’t.

Every guitarist will like a different size. And they will feel comfortable with their own ideal size. By saying that 2.8 – 3.8 is a standard size we are saying that a good average number of guitarists will like this height of the strings.

But what if you are a guitarist who plays with a lot of power and strength? Maybe this size is not for you and you want a higher height. In many cases guitarists who like and can play with strength and power like the guitar to have a rather high string height because they feel comfortable and there is less risk of buzzing noises appearing in their playing.

What if you are a guitarist who has not been playing for a long time or you simply like to play very comfortably without using effort in your left hand? Then your ideal string height will probably be a little bit less than this standard. Although the standard 2.8 – 3.8 is really comfortable.

What are the limits at which we can talk about a guitar that starts to be uncomfortable, let’s say, obviously due to its incorrect strings height?

Well, I would say for example if your classical guitar is 4mm high on the first string then we are talking about a guitar that is almost certainly very hard for anyone to play. But anyway you set the limits.

But there are limits of course.

If a classical guitar has 1.5mm of height on the first string we are talking about a guitar that most likely has problems with buzzing noises. And if it doesn’t, then you are quite lucky. And remember that with such a low action you are going to lose sound projection.

For me a classical guitar with 3.3 – 3.5mm on the first string is already high for me and I don’t feel good playing it.

And on the sixth string for me, 4.3 and above is already quite uncomfortable for me.

Now someone says to me: Alberto, I have set this standard size of 2.8 and 3.8mm on my guitar and I still find it difficult to play.

Well, the comfortable playability of a guitar doesn’t only depend on this size. But if the guitar is good in all respects with this standard size, it is quite correct to play comfortably. Then your discomfort may be due to other causes.

As we always say with the classical guitar we are talking about a very complex instrument where many parameters intervene to obtain a result or to solve a problem.  And this is so for the playability which is so important for the guitarist. For example, if your fretboard is not in the right shape it should be, then of course this has an influence on your playability. Or if your guitar neck has also a bad shape not properly design for a comfortable playability and position of your left hand or it has become deformed or warped over time more than normal. Or if the bones of both the head and the bridge are incorrectly made, or if the frets of your guitar are worn or badly set and cause noises or are too thin or in the wrong shape… And so we could be talking about many other factors that intervene. This is why we are talking about such a complex instrument, so complicated to play well and at the same time so fascinating.

How do we fix it if a string height is not the right size?

The most common way to fix this is to vary the height of the bridge bone. If the height is too high then you can continue to use the same bridge bone you have but you can lower the height by sanding it down. And if the bridge bone is too low then you have to make a new bridge bone with more height.

You have to bear in mind that for example if you want to lower the string height by one millimetre at the 12th fret, you have to double it by 2 millimetres at the bone.

This is not something you should do yourself. You have to find a guitar maker that you trust in his work and have him do it for you. Because it’s not easy and you can screw it up. You need knowledge and experience to get it right. And a piece of advice: it is always better to go down to the bone at the top to sand the top than the bottom.

So this string height measurement that we have seen here in this video is I would say the most important to know quickly about the playability of your guitar and that as we say every guitarist should know about his guitar. I hope you already know how to measure it correctly after watching this video.