Tennis String Gauge Explained

Tennis string gauge refers to the thickness of the string.

It ranges from 15 gauge (thickest, around 1.40mm) to 18 gauge (thinnest, around 1.20mm), with 16 and 17 gauge being the most widely used.

Thicker gauges last longer and offer more control, while thinner gauges provide more spin, feel and power at the cost of durability.

Choosing the right gauge comes down to balancing how you want the ball to feel off your strings against how long you need those strings to last.

US Gauge (G)	Metric (mm)	Typical Use
15	1.40	Maximum durability, controlled baseline play
16	1.28	Most common gauge, balanced playability
17	1.25	Better feel and spin, less durable
18	1.20	Maximum feel and spin, least durable

Below, this guide covers the details behind these numbers, how gauge is measured, how each thickness changes your performance, and how to pick the right one for your level.

Understanding Gauge Numbers and Measurements

US gauge numbers run counterintuitively. Lower numbers mean thicker strings, which catches out a lot of players shopping for the first time. A 16G string is thicker than a 17G, for example.

You may also see "L" next to a gauge number, like 16L or 17L. This stands for "Light" and indicates a half size between two standard gauges. It's useful when you want a middle ground without committing fully to either side.

When converting gauge to millimeters, keep in mind that industry tolerance is typically ±0.02mm. A 1.23mm and a 1.25mm string can both be labeled 17 gauge depending on the manufacturer.

This variation is standard and does not meaningfully impact playability, so focus on the gauge category rather than chasing exact millimeter readings.

You will see both systems on packaging when shopping. Metric is more precise, but the gauge number is what most players and stringers reference in conversation, especially in the US.

How Does String Gauge Affect Your Game?

Power and Control

Thinner strings (higher gauge numbers like 17G or 18G) are more elastic, creating a greater trampoline effect that returns more energy to the ball with less effort from you.

Thicker strings (lower gauge numbers like 15G or 16G) are stiffer, which gives you a more controlled, predictable response but less free power.

This is why players who generate their own pace often lean thinner for the added pop, while players who want a stable, composed response lean thicker.

Spin Generation

Thinner strings dig into the ball's felt more effectively, creating greater grip at contact and more rotational potential on every stroke.

This effect is amplified when a thin gauge is paired with a shaped string profile, such as the hexagonal profile of Zero and Vivo.

Feel and Comfort

Thinner strings absorb more impact energy before transferring it to your arm, making them a slightly friendlier choice for players with joint sensitivity or past arm issues.

That same elasticity creates deeper ball pocketing, which refers to how long the ball sits in the stringbed during contact.

More dwell time gives you a stronger sense of feel and connection with each shot. Sync 18G is designed to maximize this pocketing effect, pairing its round profile with the thinnest gauge in ReString's lineup for players who prioritize feel above all else.

Durability

As strings get thinner, their lifespan shortens. A 16G string will typically outlast an 18G under the same playing conditions.

Players who break strings frequently should factor this tradeoff seriously. The performance gains of a thinner gauge are lost if you are restringing every week.

One way to get around this is a hybrid setup, placing a thicker or more durable string in the mains (where most wear occurs) and a thinner string in the crosses for feel.

How to Choose the Right Gauge for You

Your ideal gauge depends on what you value most on court and how your game is developing.

Priority	Gauge	Reasoning
Starting Point	17	Balanced feel, spin and durability
More Feel, Spin and Power	18	Enhanced string performance
More Durability and Control	16 or 15	Longer lasting under heavy hitting

For most players, 17G is the best place to start. It offers a balanced mix of feel, spin and durability that works at every level.

As you improve and understand your preferences, you can start optimizing from there.

If you place a premium on feel, spin and power, experimenting with a thinner gauge like 18G will enhance those characteristics. You will need to accept that your strings won't last as long, but for many players the performance gains are worth it.

If durability is your priority because you put a lot of intensity into every strike, moving to a thicker gauge like 16G gives you something more resilient. You trade a bit of feel and elasticity for a string that holds up under heavy hitting.

That said, plenty of advanced players stay at 17G. ReString athlete and WTA professional Cristina Bucsa competes with a 17G Zero and Sync hybrid setup. The best way to find your ideal gauge is to experiment and let your on-court experience guide the decision.

Tips for Switching Tennis String Gauge

When testing a new gauge, change only one step at a time and play at least a few sessions before making a judgment. First impressions with a new gauge can be misleading.

When moving to a thinner gauge, you can increase tension by around 2 lbs to offset the added power. When moving thicker, dropping tension by around 2 lbs recovers some of the elasticity you lose from the stiffer string.

This is extra fine-tuning rather than a requirement, but it can make the switch feel more natural.

It also helps to track how long your strings last after each gauge change so you can weigh the performance difference against durability for your specific playing frequency.

Conclusion

Gauge is one of the most accessible ways alongside tension to fine-tune your setup. The right choice depends on what performance characteristics you want most and where your game is right now.

The good news is that ReString strings are available in a range of gauges.

Zero comes in 16G and 17G for power and spin. Sync comes in 16G, 17G and 18G for control and feel. Vivo comes in 16G and 17G for control and spin with a sustainable edge.

About the Author: Juan is the co-founder of ReString. He was born in Argentina, raised in Japan, and moved to the US to pursue college tennis. He now plays as an ATP & WTA hitting partner.