Your serve lost 3 mph last week.
Your strings died two matches ago.
Now you'll know.
Tap your strings. Get an instant tension reading from just your iPhone. Know exactly when to restring — and at what tension — so every match starts with strings that actually perform.
Your iPhone is already a
string tension meter
Cross-verified accuracy
Every reading is cross-checked by independent analysis methods for reliability. The same acoustic physics used in professional instrument tuning — now measuring your strings. Science-grade precision from your pocket.
Real-time Quality Coach
The app guides you in real time — telling you if the room is too noisy, if your tap was too soft, or if anything seems off. Bad taps are automatically rejected so you only get readings you can trust.
Three taps to precision
Hold your racquet near your iPhone, tap the strings, and let acoustic science do the rest.
Tap Your Strings
Hold your racquet near the iPhone mic and tap the string bed 3–10 times. The Quality Coach guides you in real time.
Instant Analysis
Advanced acoustic analysis captures the sound of your strings and converts it into a precise tension reading using established physics. All processing happens instantly on your iPhone.
Track & Optimize
See your tension reading with confidence score. Track decay over time. Get AI-powered restring recommendations.
Tension changes
everything about your game
String tension isn't just a number your stringer sets and you forget. It directly controls how your racquet performs on every single shot.
Power
Lower tension means more power. Strings act like a trampoline — a 4 lb drop can add measurable speed to your serve and groundstrokes.
Spin
Lower tension allows more string movement, which means more spin potential. The sweet spot depends on your string type and swing speed.
Control
Higher tension gives you a smaller sweet spot but more precision. Competitive players often trade power for placement at critical moments.
Comfort
Too-high tension sends more shock to your arm. Finding the right tension protects against tennis elbow, wrist fatigue, and shoulder strain.
You're guessing.
Every single time.
Polyester strings lose up to 10% of their tension in the first 24 hours after stringing. After a week of play, you could be 6–8 pounds below target. That's the difference between a serve that kicks and one that sits up. Between a backhand that bites and one that floats. String Tension AI shows you exactly where you stand — so you never play with dead strings again.
You've tried. We know.
"I just squeeze the strings"
The squeeze test can't detect a 4 lb difference — but your game can. Human fingers aren't tension meters. You need actual numbers, not a vague feeling.
"I restring every X weeks"
Calendar-based restringing ignores how you play, where you play, and what your strings actually need. One size doesn't fit all — and you're either wasting money or playing with dead strings.
"I bought a tension meter"
Electronic tension meters cost $200+. They give you one reading at a time with no tracking, no history, no decay prediction, and no recommendations. Your iPhone can do better.
Your strings lose tension
more than you think
After every measurement, String Tension AI tells you exactly how your strings are performing — tension loss percentage, decay rate, confidence metrics, and when you should restring.
Knows when and at
what tension to restring
The Tension Advisor analyzes your playing history, court surface, weather, arm health, and priorities to suggest the ideal tension for your next restring — with transparent reasoning.
Way more than
a tension meter
Measurement is just the beginning. String Tension AI is a complete string management platform.
📈 Know When Your Strings Die
See exactly how fast your strings are losing tension and when they'll drop below your comfort zone. The app tracks every string job and tells you the optimal day to restring — before your game suffers.
💰 Stop Overspending on Strings
Track what you spend on strings and restringing per year. See breakdowns by string type and stringer. Find out if you're restringing too early, too late, or wasting money on the wrong setup.
🏆 See What the Pros Use
Browse 50+ ATP, WTA, and legend string setups. Search by player, country, or brand. Find out what Djokovic, Sinner, and Sabalenka string at — and try their setups yourself.
⚔️ Find Your Perfect String
Compare any two strings side by side — tension retention, performance, cost per day, and annual savings. See which string actually holds up better for your playing style.
🔥 Stay Consistent, Get Rewarded
Log your sessions, build streaks, and hit weekly goals. Unlock 37 milestones across 5 rarity tiers. The more you measure, the more you learn — and the better you play.
☁️ Share With Your Stringer
iCloud sync keeps everything in sync across your devices. Export professional PDF reports or CSV data. Send your stringer exact tension specs and restring recommendations.
Physics, not guesswork
String Tension AI uses established acoustic physics — the same principles that govern musical instruments — to convert string-bed vibration frequency into precise tension readings. All processing runs on-device. Your data stays private.
In plain English: When you tap your strings, they vibrate at a specific frequency. Higher tension means a higher pitch. The app listens to that pitch and uses physics to calculate the exact tension — the same principle that lets a piano tuner know if a string is sharp or flat. For the technically curious, here's what happens under the hood.
Audio Capture
High-fidelity audio capture optimized for each iPhone model, with adaptive gain control and sub-millisecond timing precision.
Impact Isolation
Intelligent signal isolation separates string impacts from ambient noise in real time — accurate even in noisy environments like gyms and courts.
Frequency Analysis
Multi-stage frequency analysis with harmonic validation extracts the string's fundamental pitch to within ±0.5 Hz — rivaling dedicated hardware tuners.
Tension Calculation
A physics-based model converts pitch to tension in lbs, accounting for your specific string type, racket setup, and playing history through a personalized calibration profile.
From club courts
to the pro circuit
Competitive Players
It's Saturday morning. League match in an hour. Your strings were done 10 days ago — are they still good? Tap three times and know for certain. If they've dropped below your threshold, grab your backup racquet.
Coaches & Academies
Your junior player keeps shanking forehands. Dead strings or bad technique? Check their racquet in 30 seconds. Manage your entire team's string health and send restring orders with exact tension specs.
Stringers & Technicians
Give your clients something no other stringer offers: objective tension tracking over time. Share decay data that proves your work holds up. Build loyalty with science-backed service that makes you the obvious choice for restrings.
Trusted by players who
take their game seriously
"I had no idea my strings were losing 10% tension in the first week. Now I restring based on data, not guesswork. My consistency has improved noticeably."
"I coach 12 juniors. Being able to check their string tension in seconds — instead of guessing or sending them to the stringer — has been a game changer for match prep."
"My clients love getting tension reports after I string their racquets. It builds trust and they come back every time. Best tool I've added to my stringing service."
Got questions?
Stop guessing.
Start measuring.
Download String Tension AI and take your first measurement in under 30 seconds. Free to download. Free to measure. No accessories, no complicated setup, no catches.