How To Measure Guitar String Gauge: Identify Them Easily

six new guitar strings that are different gauges rolled up into circles

Guitar strings are an essential component of a guitar. For your guitar to function optimally, you must replace them now and again. How do you measure and identify the string gauge when it’s time to change your guitar strings?

To measure your guitar string gauge for easy identification, you can:

  1. Measure the strings with a digital caliper. 
  2. Check for color-coded ball ends to know the gauge.
  3. Compare the string with others of known gauge value.

Any of these steps can help you identify the gauge of your guitar strings. However, their levels of accuracy will vary depending on other factors. To help you get this right, we will discuss these different methods in detail.

1. Measure the Strings With a Digital Caliper

A digital caliper is the most effective tool for measuring your guitar string gauge. Because the gauge of the string is relatively thin, you need a tool that can measure dimensions as small as 1/1000th of an inch.

close up of a digital caliper showing a measurement in mm

Place the string to be measured between the digital caliper’s or micrometer’s external jaws and adjust until both softly clamp the string. You can then read the measurement on the digital screen. This is the only method you can use to measure guitar strings accurately.

2. Check for Color-Coded Ball Ends To Know the Gauge

Some guitar string manufacturers like Rotosound and D’addario color-code the ball ends of their guitar strings. This, however, will not apply to nylon strings. With these color-coded ball ends, you may be able to identify the string gauge. The downside is that you can only identify the string gauge if you know how the manufacturer codes the gauges.

If you tossed away the strings’ packaging ages ago, you could still replace the strings on your guitar with the strings by matching them by color. You can also skim through the string manufacturer’s website for info. However, you may not still be able to tell their exact gauge. Depending on your reason for wanting to know the gauge of your guitar strings, this method may be okay.

3. Compare the String With Others of Known Gauge Value

Another common sense approach to identifying the gauge of a guitar string is by comparing them with strings of which you already know the gauge. While possible, it will require careful observation, especially for the thinnest strings. You can use this method if all you want to do is replace your old guitar strings with new ones of the same or similar gauge.

Understanding Guitar String Gauges

Guitar strings and an orange guitar winder on white background

Now that you’re done measuring the strings and know the gauge of the strings, what do you make of the values you’ve just gotten? Your standard guitar has six strings which must all meet specific criteria to deliver the tone and playability you want from your guitar.

Guitar strings are generally broken into two broad groups. There are those designed for the electric guitar and those designed for the acoustic guitar. Each set has its gauge classification, and we will look at both shortly.

You will find string packs with gauge descriptions or actual number values. For example, you can see a pack described as medium and another with actual number values like “set of 9” or “size 9”. We will provide a chart explaining how these relate to each other.

For clarification, it is important to note that the gauge value you will see on guitar string packs will be for the thinnest or high E string. For example, if a pack is described as a “Set of 9” or “Size 9”, it means that the thinnest string, the high E, measures 0.009 inches (0.23 mm) in diameter.

Below are two charts showing the relationship between the number values and the name description:

Acoustic Guitar String Chart 

StringExtra LightCustom LightLightMediumHeavy
E.010 (.25 mm).011 (.28 mm).012 (.30 mm).013 (.33 mm).014 (.36 mm)
A.014 (.36 mm).015 (.38 mm).016 (.41 mm).017 (.43 mm).018 (.46 mm)
D.023 (.58 mm).023 (.58 mm).025 (.64 mm).026 (.66 mm).027 (.69 mm)
G.030 (.76 mm).032 (.81 mm).032 (.81 mm).035 (.89 mm).039 (.99 mm)
B.039 (.99 mm).042 (1.07 mm).042 (1.07 mm).045 (1.14 mm).049 (1.22 mm)
E.047 (1.20 mm).052 (1.32 mm).054 (1.37 mm).056 (1.42 mm).059 (1.50 mm)

Electric Guitar String Chart

StringExtra LightCustom LightLightMediumHeavy
E.008 (.20 mm).009 (.23 mm).010 (.25 mm).011 (.28 mm).012 (.30 mm)
A.010 (.25 mm).011 (.28 mm).013 (.33 mm).015 (.38 mm).016 (.41 mm)
D.015 (.38 mm).016 (.41 mm).017 (.43 mm).018 (.46 mm).020 (.51 mm)
G.021 (.53 mm).024 (.61 mm).026 (.66 mm).026 (.66 mm).032 (.81 mm)
B.030 (.76 mm).032 (.81 mm).036 (.91 mm).036 (.91 mm).042 (1.07 mm)
E.038 (.97 mm).042 (1.07 mm).046 (1.17 mm).050 (1.27 mm).054 (1.37 mm)

Note that the name descriptions may differ here and there. What we’ve described as “Extra Light” and “Custom Light” here can be described as “Super Extra Light” and “Super Light,” depending on the brand. The vital thing to note is that whatever description these two lighter gauges may have, they are the two lighter gauges above the light, medium and heavy gauges.

Why Is It Important To Choose the Right Gauge for Your Guitar Strings?

It’s important to choose the right gauge for your guitar strings because the gauge affects your guitar’s tone, playability, and play style. Some guitarists prefer thin gauges that allow for easier bending and vibrato, whereas others love the thick gauge’s meaty, bassy tone.

Let’s talk about it in more detail now:

It Will Affect Your Guitar’s Tonal Quality

The tone you will get from any guitar is determined by factors such as the wood, string type, and electronics. In general, the gauge of your guitar strings will have the following effects on your guitar’s tone:

  • Light Strings — These types of strings are easy to play. They are great for beginners because they are easy on the fingers. They will, however, not yield so much volume and sustain. The lighter they are, the more susceptible they are to breaking.
  • Medium Strings — This is a balance between the light and heavy strings. They are easier to play than the heavy strings, offer more volume and sustain than the light strings, and generally deliver a warmer tone. These are more difficult to break than light strings.
  • Heavy Strings —  You can expect very warm tones from these types of strings. They are also the most difficult to play, which is why they’re best for experienced players. You will also get the loudest volume and sustain from these strings, and they will be difficult to break while playing or tuning.

Interestingly, this effect is more pronounced with an acoustic guitar than with an electric guitar. This is because the acoustic guitar relies solely on its acoustics to deliver tone and volume, so strings greatly affect the tone. On the other hand, the electric guitar has the luxury of amplifiers and effects to modify its tone and volume.

The String Gauge Will Affect Playability

Playability refers to the ease with which a guitar can be played. This includes the intensity required to hold a string down to the fret or bend it while playing.

Light strings will generally be easier to play and bend. This is why it is usually best for beginners to go for the lightest strings. As the strings move towards the heavier gauges, they become more difficult to play. Experienced players can play them easily because they have put in years and likely have calluses that allow them to play without the inhibitions that new players experience.

It Can Enhance Your Playing Style

You should also choose your guitar string with your playing style in mind. Heavy strings are more suitable for heavy players (metal, rock, and others). These genres of music require full tones, which you can only get from heavy strings. These heavy strings are also better equipped to handle the intensity and heavy strumming associated with these types of music.

On the flip side, light players should go for light strings. These types of strings are best suited for soft music and solo playing.


We’ve taken some time to explain the issues surrounding guitar strings, how to measure a string gauge, and how to identify these gauges by comparison. With the information we’ve shared here, you hopefully now understand the importance of the guitar string gauge and how to measure your current strings.

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