How to choose a tennis string? Start from what you break
Updated: 1 hour ago
The string is the only part of your equipment that touches the ball. It is also the cheapest to change, and the one chosen with the least information: a name, a colour, and the opinion of a player whose game is not yours.
There is no best string. There is a position, on a scale, that matches what you do to the ball and what you want changed. Here is how to find it.
Why "the best string" means nothing
A string does not deliver a quality. It makes a compromise between three things that oppose each other two by two: energy return, spin potential (the string's ability to snap back after shearing across the ball), and durability.
You cannot raise all three. A very soft string returns well and wears fast; a very stiff string lasts and returns less; a smooth string snaps back well but bites less than its textured version.
That is why we numbered our range from 1 to 7 rather than giving it seven names. A string name tells you nothing. A number places it — and above all, it compares to the other six.
The four variables that decide
The material. A multifilament is made of thousands of fibres: it stretches a lot, returns energy well, and abrades quickly. A monofilament is a single strand, stiffer, more stable over time, less generous in return. It is the variable that weighs most heavily on what the arm absorbs.
The gauge, that is, the diameter. A thin gauge bites more into the ball and breaks sooner; a thick gauge lasts longer and makes the string bed duller. The right question is not actually the diameter itself, but what that diameter does to the deformation of the string bed.
The shape of the section. Round, octagonal, pentagonal, hexagonal, textured: edges bite the ball more and shift the compromise between snapback and grip. What shape really decides is subtler than "edges give you topspin".
Tension. It is not a property of the string, but it changes its behaviour as much as the other three combined. We come back to it below.
What your current string already tells you
Before choosing, look at the one on your racquet. It contains most of the answer.
It breaks in under three sessions. You produce a lot of shear. You belong in the high numbers: N°6 is the one we recommend to chronic breakers, and N°7 if control comes before everything.
It never breaks and you keep it six months. The problem is not the choice of string, it is the frequency. A string dies well before it breaks: it loses tension, deforms, and stops snapping back. When to restring is then the real question.
The main strings are deeply notched in the centre. Snapback is no longer happening. The ball leaves with less rotation, and you compensate by closing the racquet face.
Your arm pulls late in a match. Look at material and tension first, in that order. N°1 and N°2 are the two to consider, and the whole subject is covered in tennis elbow and your racquet.
The ball drops short when you brush up. Often a string that is too tight, or dead, before it is a badly chosen string.
Those five observations take thirty seconds and are worth more than any comparison chart.
Where to place yourself among the seven numbers
The range is ordered: from N°1, the softest and most generous in return, to N°7, the stiffest and most controlling. A pentagonal N°4.5 completes the scale between N°4 and N°5.
N°4 is the most versatile of the seven, and its shape is what explains it: it is octagonal, where N°5 is round. Its edges are what make the difference: for the same swing, N°4 bites the ball more, and it is that bite which makes it generous for the greatest number. N°5, smoother, is the choice of feel, control and predictability — and it lasts longer. N°4 remains the default starting point when you do not know, and the best reference: once you have played it, you know which direction to move in.
The usual path is simple. You start at N°4. If the ball lacks depth and the arm takes it badly, you go down towards N°2 or N°1. If the string moves too much, breaks too fast, or the ball leaves too easily, you go up towards N°5, N°6 or N°7.
What makes that path possible is that the seven were measured on the same bench with the same protocol: eight strings, each characterised by its elongation curves, recorded under the same conditions. That is what allows us to say one number is softer than another without using an adjective. The full reasoning is in the science of strings.
Hybrid setups, and when they actually help
A hybrid means two different strings: one in the mains, another in the crosses. The idea is to put durability and control where the wear happens — the mains, which slide — and comfort where almost nothing happens.
It works, on two conditions. The first is that you actually break mains and not crosses. The second is that you accept that the whole bed behaves like the stiffer of the two, not like the average.
A poorly motivated hybrid complicates the reading for nothing: you will no longer know which of the two strings produced what you feel. As long as you are still looking for your position in the range, stay with a full bed.
Tension decides as much as the string
The same string, strung three kilos lower, becomes a different object: contact lengthens, the ball leaves higher, the feel softens. Three kilos higher, it becomes more predictable and drier.
The usual fear — "if I drop tension I will lose control" — deserves to be tested rather than believed. In many games, a lower tension produces a higher, safer trajectory, and therefore more balls in the court. The tension question is asked backwards from the way most people put it.
One rule of method only: do not change the string and the tension at the same time. Otherwise you will not know what acted, and you will have spent two restrings to learn nothing.
Set or reel: when a reel starts to pay
A set is 12 metres — enough for one racquet. A reel is 200 metres, which is sixteen restrings.
The threshold is easy to set: right across the range, a reel costs what ten sets cost. Past ten stringings it comes out cheaper; below that the set wins — and an opened reel ages, particularly if it is stored somewhere warm. If you break every two or three sessions, or if you string for two or three players, you pass the threshold without thinking about it.
There is a second argument, less obvious: a reel commits you to one number. That is a constraint for anyone still looking for their position in the range, and an advantage for anyone who has found it. While you are exploring, buy sets; once you have settled, move to a reel.
Lifespan is not counted in hours
The rule you were taught — "restring as many times a year as you play hours per week" — is an order of magnitude, not a measurement. It ignores the string itself, the tension, the temperature, and above all what you do to the ball.
What degrades can be seen and felt.
The notches. Look at the mains in the centre of the bed. Once they are grooved, snapback no longer happens: the strings no longer return to place after shearing across the ball. You produce less rotation for the same stroke, and you compensate without knowing it.
Tension loss. Fast in the first hours, then slow. A string that has lost a lot gives a higher, longer ball — until it becomes uncontrollable.
String movement. If you have to push the strings back into place by hand on every point, the bed is no longer working as intended.
A monofilament loses its qualities well before it breaks. That is the trap for players who never break: they play six months on a dead string, then change racquets. The full subject is here.
Five choosing errors we see
Choosing a professional's string. A tour player generates racquet-head speed that has nothing to do with yours, and restrings daily. The same string in another hand is a different object.
Going stiffer to gain control. Control comes first from trajectory, so from spin, so from snapback. A stiffer string strung tighter often gives a shorter ball that is harder to place.
Changing string and tension on the same day. You will learn nothing.
Judging on the first half hour. A new string loses a noticeable share of its tension in the first hours of play. What you feel after ten minutes is not what you will play the following week.
Taking a thin gauge to "bite more" without accepting the breakage. A thin gauge does bite more, and it breaks sooner. It is a trade, not a gain.
What we do not know
We do not know which number suits you. What we do know is where each one sits relative to the other six, because we measured them under the same conditions. If you would rather have the questions asked in order, the configurator does it for you.
Start at N°4, play it for three weeks, and move one number. It is the cheapest and most reliable method there is.
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