String gauge explained: does it matter?

What gauge means

String gauge is the diameter of the string, measured in millimeters. Manufacturers also use a numbered gauge system — which runs counterintuitively: higher gauge numbers mean thinner strings. The full range used in tennis:

Gauge	Diameter	Common use
15	1.40–1.41 mm	Maximum durability; string breakers
15L	1.34–1.36 mm	High durability with more feel than 15
16	1.26–1.34 mm	Most common recreational gauge — the sweet spot
16L / 1.25 mm	1.25–1.29 mm	Common for advanced poly players; good spin/feel balance
17	1.20–1.24 mm	More feel and spin; less durable
18	1.14–1.19 mm	Maximum feel; breaks quickly; niche use

"L" stands for "light" — a half-step between numbered gauges. 15L is thicker than 16 but thinner than 15. Many poly strings are marketed by their exact millimeter rather than a gauge number (e.g., "1.25 mm" instead of "17g"), which is more precise.

What thinner gauges give you

• More feel. Thinner strings deform more on contact, giving better tactile feedback about where the ball hit and how the stringbed responded.
• More spin. Thinner strings embed slightly into the ball more, and deflect and snap back with more movement — both effects increase topspin on brushing strokes.
• More elasticity. Less material means the string bends more freely. This adds a marginal amount of power and arm comfort — though the effect is smaller than changing string type or tension.
• Less durability. Less material means the string is worn through faster by the abrasion of cross-string contact.

What thicker gauges give you

• More durability. More material to abrade through before the string breaks. The right call if you break strings every 2–4 weeks.
• More consistent performance over time. Thicker strings don't notch as quickly at cross intersections, so the playability stays stable longer.
• Lower cost over time. If you break 17g every three weeks, you might get six weeks from 15L. The per-stringing cost of 15L is the same; the annualized cost is lower.

What most players should use

16g (1.30 mm) is the starting point for most recreational players. It balances durability and feel well, has enough spin potential for any swing, and is the most widely available gauge across all string types.

How gauge interacts with string type

With polyester

This is where gauge makes the most meaningful difference. Recreational players typically use 16g (1.30 mm) for a balance of durability and feel. Advanced players often use 17g (1.25 mm) or 16L (1.28 mm) to add feel and spin. Tour players sometimes go to 1.20 mm for maximum spin bite, accepting that the string breaks faster.

Going thinner with poly also makes the string slightly more elastic — which marginally reduces arm stiffness. If you're on full poly and your arm is bothering you, going from 16g to 17g is a small improvement. Going from poly to multifilament at any gauge is a much larger one.

With natural gut

17g gut (1.25 mm) is a common choice for feel-oriented players. 16g gut offers meaningfully better durability — gut is already very elastic, so you don't need to go thin for feel. We rarely recommend 18g gut for recreational players; the string life is very short and the benefit over 17g is marginal.

With multifilament

16g is standard. Multifilament is already soft and elastic — gauge matters far less here than with poly. Unless you're breaking multifil frequently, there's little reason to move away from 16g.

A note on string-breaking diagnosis

If you're breaking strings in the mains and the solution feels like "go thicker," that's not always right. The real cause is usually the combination of swing mechanics, string type, and string movement at cross intersections. A thicker poly will last longer — but it will also be stiffer and harder on your arm. Sometimes the correct fix is a different string type at your current gauge rather than a thicker gauge of the same string.

Come in and we can look at the wear pattern — where the string breaks tells us a lot about why it's breaking and what will actually fix it.