Tennis String Tension App for iPhone
String Tension AI helps tennis players measure racquet string tension from their iPhone, track tension loss over time, and know when it is time to restring.
Tap your stringbed, let your iPhone analyze the stringbed vibration, and get a tension reading in seconds. Then keep measuring after restringing, practice sessions, matches, and weeks of play so you can see how your strings are actually changing.
Free core measurements · No external hardware · Built for tennis players who want better restring decisions from real measurement history.
String Tension AI is an iPhone app for tennis players who want to measure racquet string tension, track tension loss over time, and decide when to restring.
The app uses iPhone audio analysis to evaluate stringbed vibration after the player taps the strings.
String Tension AI is best used as a tension tracking and racquet management tool. Players can build a fresh-string baseline, measure after matches and practice, and compare tension trends across string setups.
The goal is not just one reading. The goal is a personal racquet history that shows whether strings are holding tension, dropping normally, or ready to restring.
Why use a tennis string tension app?
Most players know when their racquet feels different. The problem is that "different" is hard to measure.
Maybe your shots are flying long. Maybe your spin feels inconsistent. Maybe your poly strings feel dead, but they have not broken yet. Or maybe you just restrung and want to know how quickly your setup loses tension.
A tennis string tension app gives you a repeatable way to track that change. String Tension AI is built for one job: helping you understand what happens to your racquet between restrings. With regular measurements, you can:
- Build a fresh-string baseline for each racquet.
- Track tension loss after matches and practice.
- Compare different string setups.
- See whether your racquet is still in your preferred range.
- Make smarter restring decisions.
- Learn how many playing hours you get from each string job.
- Track string cost per hour over time.
Measure your racquet from your iPhone
String Tension AI uses your iPhone microphone to analyze the sound of your stringbed vibration. The flow is simple:
- Open the app.
- Hold your racquet near your iPhone.
- Tap the strings.
- Review the measurement quality.
- Save the reading to your racquet history.
No clip-on sensor. No separate tension meter. No extra accessory. The app gives measurement quality feedback so you know whether the tap, background noise, and signal were good enough to trust for consistent tracking.
How much tension do tennis strings lose?
String tension loss is one of the most overlooked factors in tennis performance. From the moment your racquet leaves the stringing machine, your strings begin losing tension — and the rate depends on string material, gauge, strung tension, and how often you play.
Polyester (co-poly) strings are the most popular choice among competitive players, but they also lose tension the fastest. Most polyester strings drop 10–15% of their tension within the first 24 hours after stringing, before a single ball is hit. Over the following weeks, tension continues to decline with every hour of play.
Natural gut holds tension significantly better than polyester, which is one reason tour pros have historically used gut in hybrid setups. Multifilament and synthetic gut (nylon) fall somewhere in between.
All tennis strings lose tension, with much of the loss occurring during and shortly after stringing and during the first hits; polyester generally loses more tension than nylon or natural gut. That is exactly why tracking your own racquet history is more useful than relying on a single universal rule.
Most players have no way to see this change happening. That vague feeling that the racquet "plays different" is often the only signal — and by then, tension may have dropped well below the player's ideal range. String Tension AI makes this invisible process visible. Fresh-string detection identifies your post-restring baseline, and tension tracking shows the week-over-week decline on a chart.
| Fresh strings | Strings ready to track or replace |
|---|---|
| Closer to your fresh-string baseline | Below your preferred tension range |
| More predictable response | Shots may start flying long |
| Easier to trust in matches | Control may feel inconsistent |
| Useful baseline for tracking | Better judged with measurement history |
| Good time to calibrate and measure | Good time to compare cost per hour |
The goal is not to chase a perfect number. The goal is to know when your racquet no longer feels or measures the way you want it to.
String Tension Decay Calculator LIVE
See how different string types lose tension over time based on your playing frequency. For the most accurate trend, measure your own racquet in String Tension AI.
Estimates based on general tension loss data. Your actual results depend on string brand, racquet, and conditions. Use String Tension AI for measurements based on your real setup.
When should you restring your racquet?
You should restring when your racquet has moved out of your preferred performance range — not just when the strings break. That range is personal. It depends on your string type, reference tension, swing speed, playing frequency, comfort needs, and how sensitive you are to changes in control, power, spin, and feel.
The most common rule of thumb is to restring as many times per year as you play per week. Play three times a week? Restring at least three times per year. But this does not account for string type, playing intensity, climate, or personal tension preferences. Players using polyester strings and playing frequently often need to restring far more often.
Common signs your strings may be ready to restring:
- Your shots are flying long.
- Control feels less predictable.
- The stringbed feels dull or inconsistent.
- You are adjusting your swing to compensate.
- Your current tension is below your preferred range.
The better approach is measurement. Instead of relying on feel or calendar-based rules, measure your string tension regularly and track the trend. String Tension AI helps you set a baseline immediately after restringing, track tension loss session by session, set a personal target range and get notified when you drop below it, compare how long different setups last, and use the Tension Advisor (PRO) for personalized restring timing.
When you have actual measurement data, restringing stops being a guess and becomes a decision backed by your own racquet history.
How many hours do poly strings last?
There is no single number that fits every player. Poly string lifespan depends on swing speed, string model, gauge, tension, court conditions, and your tolerance for changes in control and feel. For most players, polyester strings deliver their best performance within a window of approximately 10 to 25 hours of active play.
After that window closes, the string's elasticity is significantly reduced. Shots that used to land with controlled depth may start sailing long. The crisp, connected feeling at contact gives way to a "boardy" or "dead" sensation. Arm discomfort can increase as the string loses its ability to absorb shock.
The challenge is that this degradation happens gradually. There is no single moment when the string "dies" — it is a slow decline that many players only notice after it is well underway. The better method is to track playing hours and tension loss together, then learn when your specific setup stops feeling match-ready.
Use the calculator above to model how quickly different string types lose tension based on your weekly playing hours. Then download String Tension AI to measure your actual racquet and build your own data.
What tension do the pros use?
Professional tennis players choose their string tension based on the balance of power, control, spin, and feel they need. Most tour players string between 40 and 65 lbs, with the majority falling in the 48–60 lb range. Here are some notable examples:
| Player | String Setup | Tension (M / X) | Type |
|---|---|---|---|
| C. Alcaraz | Babolat RPM Team | 55 / 53 | Poly |
| J. Sinner | Head Hawk Touch | 62 / 62 | Poly |
| I. Świątek | Tecnifibre Razor Code | 53 / 53 | Poly |
| C. Gauff | Luxilon ALU Power | 53 / 53 | Poly |
| N. Djokovic | Babolat VS Touch / Luxilon ALU Power Rough | 59 / 56 | Hybrid |
| R. Federer* | Wilson Nat. Gut / Luxilon ALU Power Rough | 58.5 / 55 | Hybrid |
* Retired / historical setup. Tensions are approximate and based on publicly reported data. Some string links are affiliate links — we may earn a small commission at no extra cost to you. Browse 65+ full pro setups inside the app.
Pro tensions are not directly prescriptive for recreational players. Pros have their racquets restrung before every match — sometimes multiple times per day at Grand Slams. Their setups are optimized around the assumption of near-fresh strings. For club and league players who restring less often, understanding how tension drops over time is arguably more important than picking the "right" starting tension. String Tension AI helps you track both.
Track tennis string cost per hour
A restring is not just a performance decision — it is also a cost decision. If a string job costs $40 and gives you 10 strong playing hours, that is $4.00 per hour. If another setup costs $55 but gives you 22 strong playing hours, that is $2.50 per hour. The difference adds up fast for frequent players.
String Tension AI helps players connect tension history, playing sessions, restring cost, and string lifespan so they can make better equipment decisions over time. PRO includes full cost analytics — tracking restring expenses, string costs, stringer fees, and cost-per-hour calculations across all your racquets and setups.
Free to start, deeper with PRO
Start free with unlimited core measurements. Track your current racquet, build a recent history, and learn how your strings change over time.
PRO unlocks the full racquet intelligence layer:
- Unlimited racquets and string setups
- Full measurement history
- Predictive tension insights
- Tension Advisor
- What-if scenarios
- Tension targets and reminders
- Advanced string recommendations
- Hybrid builder
- String comparison
- Playing analytics
- Cost analytics
- PDF and CSV exports
- iCloud sync
Whether you play once a week or compete year-round, the goal is the same: stop relying on feel alone and make smarter restring decisions from real measurement history.
Got questions?
Know What Your Strings Are Doing
Your strings change every time you play. Now you can track it. Measure your racquet from your iPhone, follow tension loss over time, and know when it is time to restring.
No accessories · Free core measurements · First reading in seconds