As if choosing a tennis string wasn't difficult enough already due to the wide array of choice, once you've picked a string, there's another factor to think about: it's gauge.
In this guide, we'll explore what string gauge means, how it’s measured, assess how the gauge impacts its performance, look at what gauge the pros use, and help you identify what string gauge you should use.
What is Tennis String Gauge?
Tennis strings are made in different thicknesses, called gauges. The thicker the gauge or diameter of the string, the more durability, and control, while the thinner the gauge, the more power and comfort.
While there's no lower or upper limit for what the gauge of a string can be (of course it has to fit through the grommet hole in the racket) tennis string gauges typically range from 1.05 mm to 1.41 mm. The most commonly available are between 1.20-1.30 mm.
Along with the millimetre measurement widely used in Europe, tennis string thickness is communicated by a whole number. In the USA, the lower the number, the thicker the gauge. In Europe, the higher the number, the thicker the gauge.
To further complicate matters, some gauges will have an “L” besides many of the gauges. The “L” stands for “Light”. and means it's thinner. So a 15L is thinner than a 15 gauge, but not quite as thin as a 16. Likewise, a 16L is thinner than a 16 but not quite as thin as a 17 and so on.
Tennis String Gauge Chart
The USRSA has attempted to publish a broad standard for string gauge which you can see in the table below. It outlines the USA string gauge, the size in millimetres, and its European equivalent.
String Gauge Chart
|USA Gauges||Millimetres||European Gauges|
|13||1.65 – 1.80mm||12|
|14||1.50 – 1.65mm||11|
|15||1.41 – 1.49mm||9.5|
|15L||1.33 – 1.41mm||9|
|16||1.26 – 1.34mm||8.5|
|16L||1.22 – 1.30mm||8|
|17||1.16 – 1.24mm||7.5|
|18||1.06 – 1.16mm||7|
|19||0.90 – 1.06mm||4|
|20||0.80 – 0.90mm||3.5|
|21||0.70 – 0.80mm||3|
|22||0.60 – 0.70mm||2.5|
While this chart is both accurate and useful, tennis string gauge is not a universally agreed standard, which means that string manufacturers are essentially a law unto themselves.
So while the packet might say 16L, what does that really mean? It means that it falls into a broad range of diameters that can vary widely. While one company may call a 1.24mm string 16L, another may call it 17. So there's no real consistency as there is some overlap between gauge measurements.
In the picture below, you can see how Gamma Professional and Solinco Confidential, are both 16 gauge, but the thickness in millimetres is different: 1.32mm vs 1.30mm.
So if in doubt, use the millimetre measurement to know it's true gauge.
Many manufacturers tend to copy each other, so this simplified chart will capture most string producers' gauges.
Simplified Tennis String Gauge Chart
|15L||1.34mm – 1.40mm|
|16||1.29mm – 1.33mm|
|16L||1.26mm – 1.28mm|
|17||1.23mm – 1.25mm|
|17L||1.19mm – 1.22mm|
|18||1.13mm – 1.18mm|
|18L||1.08mm – 1.12mm|
|19||1.02mm – 1.07mm|
String Gauge and Performance
So we know that strings come in different gauges, but how and why does the thickness of a string impacts performance?
- Generate more power
- Generate more spin
- Have less durability
- Have more comfort
- Lose tension faster
- Generate less power
- Generate less spin
- Have more durability
- Have less comfort
- Lose tension slower
The thicker the string, he more durable and long-lasting it will be. This is because that when the strings rub against each other, they wear out, and eventually break. So naturally, the more material there is to withstand that friction, the longer it will last.
Thicker strings also handle harsher impacts better, so mishits near the frame's edge are less likely to break a string when the gauge is thicker.
Remember that the type of string has a far bigger impact, so a 19 gauge polyester is still more durable than a 16 gauge natural gut. The best way compare gauge is to look at identical strings or the very least in the same family, e.g. monofilament polyester strings.
|Property||Solinco Hyper-G 16||Solinco Hyper-G 18 (1.15)||Difference %|
|Tension Loss (%)||26||28||8%|
|Energy Return (%)||89||88||-1%|
|String to String Friction (COF)||0.09||0.082||-9%|
|String to Ball Friction (COF)||0.631||0.617||-2%|
Using the Solinco Hyper G comparison table above, you can see the thinner the string, the more spin potential, while the thicker the string has the less spin potential.
This is because thinner strings can get more of a purchase on the felt and grab the ball, which results in more spin. A thicker string bites less into the ball, resulting in a lower potential for topspin. Thinner strings are also spaced out just a tad further, and less material = less friction, creating more snapback.
However, just like durability, there are many factors at play, a thin string does not guarantee spin, but it does mean that all things equal if you hit two identical shots, the thinner gauge string will impart more spin on the ball.
Thinner strings of the same type are more elastic so therefore produce more power due to more ball pocketing.
Feel is certainly one of more subjective elements, but most players find thinner strings offer them more feel. Generally, the string will be slightly softer, and that ball pocketing gives players that more connected feeling.
Which String Gauge Should You Use?
Like most things with tennis, the gauge you use purely boils down to personal preference, and it's one of many things you can experiment with.
I break down gauges below and who they will suit.
Just remember that the type of string you use plays a big part, so if you're breaking natural gut after 5 games, moving down a gauge isn't going to really help you out that much, you'll need to switch to a more durable string and pick the thickness accordingly.
- 15/1.40mm: Thick gauge; players who want maximum durability and control.
- 16/1.30mm: Medium-thick gauge; a good choice for frequent string breakers.
- 16L/1.28mm: Medium gauge, suits players looking for a blend of power and control.
- 17/1.25mm: Medium thin gauge; for players who are looking for power and comfort.
- 17L/1.20mm: Thin gauge; for players looking for increased touch and feel.
- 18/1.15mm: Thinnest gauge; for players wanting maximum touch and feel.
I believe most players should use the thinnest gauge string that gives them adequate durability. Many players will be fine using a 17 gauge string and that is where I would recommend starting.
If you break that too easily, go to 16. If you don't break that, you could even go to 18 as a test to see if the increase in comfort, power and feel makes a difference.
At the time of writing, I use Tecnifibre Triax in 16 gauge / 1.33mm and although I don't break it, I don't feel the need to change to a thinner gauge.
What Gauge String Do Tennis Pros Use?
|Roger Federer||Babolat VS 16||Luxilon ALU Rough 16L|
|Rafael Nadal||Babolat RPM Blast 15L||Babolat RPM Blast 15L|
|Novak Djokovic||Babolat VS 16||Luxilon ALU Power 16L|
|Daniil Medvedev||Tecnifibre ATP Razor Code 17||Tecnifibre ATP Razor Code 17|
|Dominic Thiem||RPM Power 17||RPM Power 17|
|Alexander Zverev||Head Hawk Touch 17||Babolat VS 16|
|Serena Williams||Wilson Natural Gut 16||Luxilon 4G 16L|
|Naomi Osaka||Yonex Poly Tour Strike 16L||Yonex Poly Tour Strike 16L|
Frequently Asked Questions
Which tennis string gauge is best for arm friendliness?
Thinner gauge strings are better for the arm. However, the type of string you use has a much bigger impact on comfort. Before looking at the gauge, I'd look at string type. Is your elbow, wrist or shoulder in bits and you are using polyester? Then moving to a thinner gauge likely won't help. Go to a softer poly or a multifilament.
Switching gauge only really makes sense for comfort when you only need a slight adjustment. For example, you are playing pain-free but start to feel it in the arm after a long-hitting session. Maybe then a thinner gauge will make a difference.
What gauge of tennis racquet string is good for spin?
A thin gauge polyester has the most spin potential out of any string. For example, Babolat RPM Blast 18 Gauge has very high spin potential. The downside is that it will break quickly for some players.
How does tennis string gauge affect string tension?
The thicker the string, the longer it holds tension. This is because they do not stretch as much as thinner strings and consequently holds tension better. As a result, a thicker gauge string may feel at a higher tension relatively, even if it was strung at the same tension as a thinner string.
What gauge polyester tennis string is best?
The best gauge polyester string is one that doesn't hurt your arm and doesn't break after a few games. Depending on your game that could be one of several but I would start with a 16 gauge and see how you get on.
Hopefully, this post has given you a good idea of how gauge effects playability. Generally speaking, they are only very subtle differences, and my recommendation would be to use the thinnest string you can that still offers you the playtime (durability) you are after. The slight drop-off in durability from a thinner string shouldn’t be a big deal for most players and the added comfort is always a benefit.
Find Your Ideal Tennis String
Are you looking for a new string to try in your racket? Use our easy to use tennis string finder tool. It lets you filter by string type, gauge, colour, price, stiffness and shape.
What gauge tennis strings are you using, and why? Can you notice the difference when changing gauge? Let me know in the comments.