RPM Meter: Tachometer App

Turn your phone into a contactless tachometer. RPM Meter listens to a spinning part with your microphone, reads the frequency, and shows the rotation speed in RPM — no contact strip, no reflective tape, no extra hardware. WHO IT'S FOR • HVAC techs — check blower wheel and condenser fan speed on a service call • Auto and small-engine work — belt-driven accessories, cooling fans, shop tools • Woodworkers and machinists — verify spindle, router, and lathe speed settings • Makers and drone builders — prop and brushless motor RPM • Anyone replacing a fan or motor and needing a quick speed check WHAT YOU GET • Live RPM reading straight from the sound the part makes • Frequency spectrum view so you can see the dominant tone you're locking onto • Pulses-per-revolution correction — set blade count or motor poles for a correct reading • Current, max, and average for the session • Hold to freeze a reading, then Save it • Recent measurements stored on your device with the conditions (Hz and pulses per rev) so a later check is actually comparable • Light and dark themes, no account, no sign-up HOW TO USE IT 1) Tap Start measuring 2) Get the mic close to the spinning part, somewhere reasonably quiet 3) Set "Pulses per revolution" to the blade count or motor poles — a 4-blade fan read at 1 will show 4x the real speed 4) Tap Hold to freeze the number, then Save to keep it WHERE IT WORKS BEST Exposed, steady, audible rotation. Box fans, ceiling fans, blower wheels, bench grinders, drill presses, lathes, drone props, small motors. The clearer the rotation sounds to your ear, the better this works. WHERE IT WON'T WORK Be straight about this before you download: a sealed car engine is hard to read by sound. So is anything buried behind a housing, drowned out by other machinery, or spinning too quietly to hear. This is a sound-based estimate, not a calibrated laboratory instrument. Use it as a field check, not for compliance or certification work. ACCURACY NOTES Readings depend on what the microphone can actually hear. Background noise, distance, and the type of part all matter. If a number looks like a multiple of what you expect (double or half), your pulses-per-revolution setting is usually the reason — a fan's blade count is the most common cause. PRIVACY The microphone is used only to analyze sound in real time on your device. Nothing is recorded, stored, or uploaded. Measurements you save stay on your phone. Free, supported by banner ads. No account required.