Watch Timegrapher

It times every tick it hears and fits them all together, so in a quiet room the rate settles within a few seconds and a plus or minus band shows how tight it is. A phone mic is less controlled than a bench timegrapher, and a phone's sound clock can be very slightly off, so treat readings as estimates. Pro lets you calibrate against a known reading.

Rest the watch on the phone near the mic in a quiet room, and keep a metal bracelet from rattling on the table. A contact mic can help with quiet watches.

Mechanical watches from 14,400 to 43,200 beats per hour. It finds the beat rate for you, or you can pick it. Quartz watches tick once a second, and the app is made for mechanical ones.

No. Amplitude needs the separate sounds inside each tick to be timed very cleanly, which a phone mic cannot do reliably, so the app leaves it out. A watchmaker can check amplitude.

Beat error on every reading, listening past 60 seconds, a guided six position test with the average and the spread, a watch log with rate history for each watch, calibration for your phone, and clean cards with skins. It is a one-time unlock with no subscription.