Know Your
String Tension

Measure racquet string tension in seconds using your phone's microphone — and track tension loss during live matches with the camera.

🎾 Tennis 🏸 Badminton 🎙️ Microphone Analysis 📸 Live Match Monitor Free to Download

STRING TENSION

54.5 lbs

24.7 kg

Standard

🎙️ Analysed from vibration frequency · 676 Hz

Two Powerful Tools

String Meter combines acoustic physics and computer vision to give you insights no traditional gauge can match.

🎙️

Static Tension Measurement

Tap the strings near your phone, and String Meter uses the microphone to detect the vibration frequency. Physics does the rest — delivering an accurate lbs and kg readout in under 5 seconds, without any external hardware.

Tennis Badminton

How to Measure String Tension

No special equipment needed — just your iPhone.

Select Sport & String

Choose Tennis or Badminton, set the head shape (Oval or Isometric), and enter your string gauge in millimetres.

Allow Microphone

Grant microphone permission when prompted. String Meter needs the mic to listen to the string vibration — no sound is ever recorded or stored.

Tap the Strings

Hold the racquet near your phone and tap the string bed 4–5 times firmly with the heel of your palm. Keep the racquet still.

Read Your Tension

The app analyses the resonant frequency and instantly shows the string tension in lbs and kg, along with a Low / Standard / High rating.

Save to Racquet

Log the result to your racquet's history. Track how tension changes over time and know exactly when your strings need replacing.

Save Every Measurement

Every tension reading can be saved to a racquet profile. Track how your strings age over time, compare measurements across sessions, and know exactly when tension has dropped enough to warrant restringing.

Each racquet stores its full measurement history, the current string setup, and any archived setups you've retired. You can also share your result directly from the measurement screen.

📁 Multiple racquets with named profiles

📈 Full measurement history per racquet

🪤 String setup archive — track past setups

🔄 Restore a past string setup in one tap

📤 Share your tension result with others

📏 Reference tension stored per setup

Racquet & String Management

One place for everything you need to know about your equipment.

🎾 Racquet Profiles

Add your racquets with brand, model, head size, string pattern, and length. Give each one a nickname so you can identify them at a glance.

🪢 String Setup Tracking

Log the strings you're currently using — brand, model, material (Polyester, Nylon, Natural Gut, Multifilament), and gauge. Supports hybrid setups with different main and cross strings.

📦 Setup Archive

When you restring, archive the old setup with its full measurement history. All past tension readings stay attached to the string setup that produced them.

🔄 One-Tap Restore

Changed your mind? Restore any archived string setup back to active status. The current setup is automatically archived so nothing is ever lost.

📊 Measurement History

Every saved tension reading shows the date, frequency, string gauge, sport, and lbs/kg value. Scroll back through your full history to spot trends.

🎯 Reference Tension

Set a reference tension for each string setup so you always know what your stringer targeted — and how far your strings have drifted from that value.

Everything You Need

Thoughtfully designed for serious players and coaches.

📡 Acoustic Physics Engine

String tension is directly proportional to the square of the vibration frequency (f² ∝ T). String Meter measures this frequency using your iPhone's microphone with a custom FFT pipeline — no external sensor required.

🤖 CoreML Player Detection

Apple's Vision framework detects players in the camera frame. Each player is locked with a colour signature via a Lightweight Appearance Re-ID system, preventing label swaps even when players cross sides.

📈 Frequency Trend Chart

The Live Monitor displays a real-time scatter chart of hit frequencies for each player, colour-coded by player label. Watch tension drift unfold shot by shot.

🌊 Live Waveform

A real-time spectrum analyser visualises the audio input while the microphone is active — both during static measurement and live monitoring sessions.

📳 Sound & Haptic Feedback

Crisp haptic and sound feedback on every significant action. Toggle sound and vibration independently in Settings to match your preference.

⭐ Premium – Remove Ads

An optional subscription removes all ads. Monthly and yearly plans available. Premium status is verified on launch so your experience is always uninterrupted.

Frequently Asked Questions

How accurate is the microphone-based tension measurement?

String Meter uses a high-resolution FFT (Fast Fourier Transform) to detect the string's resonant frequency. Accuracy is typically within 1–2 lbs of a physical gauge when the strings are tapped firmly and the phone is held close. For best results, repeat the measurement 3–5 times and average the readings.

Which sports and string types does it support?

String Meter supports both Tennis and Badminton. Any string material (Polyester, Nylon, Natural Gut, Multifilament) and any gauge can be measured. For the best frequency reading, make sure you enter the correct string gauge before measuring.

Is String Meter free?

Yes, String Meter is free to download. The free version is supported by ads. An optional Premium subscription removes all ads. Monthly and yearly plans are available from the Settings screen.

Can I use it without internet access?

All tension measurement and racquet management features work fully offline. An internet connection is only needed for ad loading and Firebase analytics (neither blocks app functionality).

Know YourString Tension