Racketmeter lets badminton players measure string tension using the sound frequency produced when tapping the racket strings. It's 100% free, works in your browser on mobile and desktop, and requires no sign-up or installation.<p>I built it to solve a personal problem. I started playing badminton regularly in 2016 and quickly learned that players often ask stringers to string rackets at specific tensions (like 22 or 26 lbs). But after a few stringing jobs, I began to feel like the tension was inconsistent. Other players told me they just tap the strings and go by ear where "sharper sound meant higher tension."<p>One day while tuning my guitar, I could see exact sound frequencies on my tuner app. That’s when it clicked. It should be possible to build a tuner for badminton strings as well!<p>I searched online and found some tension-frequency data shared by professional stringers, but it wasn’t clean or comprehensive. So I visited 5 or 6 local stringers, gave them a frequency measuring app, and asked them to record racket head size, string thickness, tension, and sound frequency for each job. Some asked for a small payment, but most helped for free. Within a week, I had over 200 solid data points.<p>I trained a simple regression model using that data and validated it with newly strung rackets. It turned out to be surprisingly accurate. I shared it with friends and fellow players, and it started to spread in badminton forums.<p>There was another app that launched a few months later with big celebrity endorsements, but it was less accurate, harder to use, and required in-app purchases. Mine wasn't built to compete, but it ended up being more useful.<p>I originally released it as a mobile app, but constant changes in Google Play policies kept taking it down. So I rebuilt it as a simple browser-based tool.<p>Would love feedback, suggestions for improvements, or ideas on how to sustain it without cluttering it with ads or paywalls.<p>Let me know what you think.