Tennis Strings

Tennis String Gauge Explained

How does string thickness affect playability? What gauge tennis string should you use?

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.

Let's go.

What is Tennis String Gauge?

Vernier 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

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.

Gauge Difference

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

Gauge Millimetres
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

Federer Forehand Basel 1R 2018

So we know that strings come in different gauges, but how and why does the thickness of a string impacts performance? 

In summary:

Thinner strings:

  • Generate more power
  • Generate more spin
  • Have less durability
  • Have more comfort
  • Lose tension faster

Thicker strings:

  • 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.

A useful tool for this is the Tennis Warehouse string comparison tool. You can see an example of the data below for Solinco Hyper G.

Property Solinco Hyper-G 16 Solinco Hyper-G 18 (1.15) Difference %
Material Polyester Polyester  
Stiffness (lb/in) 219 180 -18%
Tension Loss (%) 26 28 8%
Energy Return (%) 89 88 -1%
Spin Potential 7 7.5 7%
String to String Friction (COF) 0.09 0.082 -9%
String to Ball Friction (COF) 0.631 0.617 -2%

Spin Potential

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?

Triax Stringing

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?

Player Mains Crosses
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.

Final Thoughts

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

tennis string finder

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.


Huge fan of Roger Federer. I watch all his matches from Grand Slam level right down to ATP 250. When I'm not watching or writing about tennis I play regularly myself and have a keen interest in tactics, equipment and technicalties of the sport.

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  1. With all that’s going on in AO as well as players and team members getting COVID, perhaps Roger’s move to skip AO, whether it was for form reason or for the whole family and quarantine saga, will turn out to be a rather smart choice.

    1. Of course it was nothing for Federer. I have seen Serena with daughter (must have been a special exempt), but imagine Federer to sit 14 days without possibility of leaving a room with Mirka and 4 children. I guess, Craig told him, how it can look like and his decision was peRFect. The only privilege he could get would be to belong to 50 persons group accommodated in Adelaide, not in Melbourne, with the luck, no positive case on the plain.
      They are all cleared now to go for 5 hours a day for training and practicing. Still not enough for family with 4 children.
      Only 1 player tested positive (Pospisil) but about 70 are strictly quarantined for 14 days. Cuevas showed good spirit and is inventing special routines to train in the hotel room . but others are only frustrated.
      To be just one must take into account, some Australian citizens are stranded in different corners of the world since almost a year because of strict rules of passing Australian border.
      With this rules they should have cancelled AO (rather AC = Australian Closed) and play instead an Australian Championship or something.

      1. I don’t think Pospisil tested positive, he was just on a plane with someone that did?

        Sandgren was positive but again this shows the huge flaw with PCR – it does not show if you are infectious. Sandgren had covid in November, I dunno if he had symptoms.

  2. Just wishing to let you know that you misspelled Alexander Zverev’s name wrong, unless Zveerev is how you spell it in Europe 😉

  3. for thin gauged Strings like 19 gauge or 18 what do you think is a proper tension, higher or lower?

    1. Hi,

      Higher or lower compared to another string or just in general? In general, it is a personal preference. If you are changing from a 15 to an 18 gauge of the exact same string, then a slightly lower tension would be technically the ‘right’ answer due to the linear density.

      But does it make a difference? I don’t think there is a proper answer. If I was moving from a 17 to an 18 gauge, I wouldn’t change it. It is just a case of testing it and seeing if you feel like you notice a difference and need to go higher or lower. Personally, I don’t think I would notice.

      I think for most players, small changes in tension are not going to be noticed. I mean most recreational players will string a racquet and then not play with it for at least 24 hours, so what even is their tension? I think if you have a reference tension and when you play with the racquet it’s in and around that figure, then all good.

      And to be honest, even for most pros, they wouldn’t know. I remember hearing an interview with Richard Parnell once when he had strung a racquet for a player at a tournament, they came in, banged it on the palm of their hand and told him it was too tight and instructed him to redo it. Parnell said ok and told him to come back in 30 minutes, but all he did was leave the racquet, knowing all the while it’d be losing tension and when the player came back, did his palm banging thing again, he was like 👌 perfect.

  4. nice summary – I play with a gut (mains) / poly (Crosses) hybrid and generally really like the set up. However, I was looking for a touch more spin. I think changing the gauge might be a good tweak (currently using a 16 gauge on both).

    Which should I change the gut or the poly to get the most impact… or does it matter ?

  5. thanks for the response – interesting… in a hybrid set up which is the more dominant, i.e the mains or the crosses?

    or, maybe more generally what are the various advantages/disadvantages of having poly in mains vs gut in the mains (for a poly/gut hybrid)

    BTW – love the site, some really great info

  6. Thank you for your in depth analysis and explanations and string finder. I have generally used Babolat Pro Hurricane 16/130, but lately confused by the many variations and not knowing the differences. Great help.

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