What is ukulele 'action'?

14 Jul 2011

What is ukulele 'action'?

This is a jump back to some basic stuff, but it struck me that whilst I had described action in some other beginner tip posts, I had not described what the term 'action' means on a ukulele in a dedicated post. So, here we go!

The term 'action' means the way the strings of the ukulele relate to the fingerboard. That is to say, the angle and height of the strings in relation to the straight fingerboard.

You will hear of poor action as being either high or low, and they each create their own problems.

1. A high action affects playability (the way the uke feels and how easy and fast it is to play) as well as intonation ( see Here. And Here for more on that) which basically relates to how accurate the instrument is in tune down the neck.

2. Low action will cause buzzing as the strings are too low and close to the frets and in extreme cases, may actually be incapable of tuning if the string is actually ringing between, say, the first fret and the bridge as opposed to being between nut and bridge.

In respect of the former, playability is bad enough and will lead to aching sore fingers, but if the strings are high at one end, you will create intonation problems.

Like it or not, a stringed instrument is a mathematical thing. That taut string requires itself to be as parallel as possible to the fingerboard in order that when fretted, the corresponding fret creates the right note. If you imagine a very high bridge, the string will get closer and closer along its length to the fingerboard as it approaches the nut. In other words, it is the hypotenuse of a long thin triangle. Raise the bridge too high, and your mathematics knowledge will tell you that the hypotenuse will lengthen. The fret placement relies on the length of the string between nut and bridge measured in a straight line to be fixed. Raise the bridge, you lengthen the hypotenuse and throw out the mathematics! The result is that the notes that ring at certain fret positions will be out.

A high nut can create the same thing on it's own, but more commonly will manifest it's problem in tuning at the first and second frets. A string leaving a high nut when fretted at the first requires the string to be pulled down too far from it's horizontal and this too lengthens that hypotenuse and throws out the tuning.

My intonation links above deal with tracking down the issues on intonation which is often due to action, but bear in mind, you can have a high action with no intonation issues (ie where nut and bridge are too high together at a level that doesn't make that hypotenuse too long)

So what makes the right action? Well that depends on your style, but mine currently measure between 1/8 and 3/16 of an inch between the string and the top of the crown of the 12th fret.

If in doubt, speak to a guitar tech or luthier!

- Posted using BlogPress from my iPad


  1. i found an easier way to check the action is to drop a un-embossed credit card or similar between the fretboard and the strings whilst holding the uke upside down. the card should not pass the first fret and ideally stop around the second or third.
    theres nothing more off putting than a high action, it discourages new players!


  2. Barry
    Is it not the case that very ukulele's action is higher closer to the body than it is as As the strings approach the neck?

  3. Yes David - higher at the bridge than the nut. If either one is too high it will throw off the tuning


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