Beat Error
Beat Error app icon

How accurate is your watch? Ask your iPhone.

Lay your iPhone next to your mechanical watch. Its microphone hears the ticking and shows the rate in seconds per day, beat error and amplitude in about 30 seconds. No account. No server. Works offline.

Coming soon to the App Store
An iPhone lying flat next to a watch on a folded towel
Beat Error measuring a watch: +4.1 seconds a day, plus or minus 0.6, strong signal, beat error 0.3 ms, amplitude 283 degrees

How it works

Place the iPhone flat with its bottom edge touching the crown.

Keep still for 30 seconds.

Read rate, beat error and amplitude.

Honest numbers

Readings are estimates from the phone's microphone, not a bench timegrapher. Every number comes with its uncertainty.

STRONG signal
Can't hear the watch yet.
Move the crown closer to the bottom edge.

What it does

Bench readings

Rate, beat error and amplitude from the iPhone microphone in about 30 seconds, with a live timegraph.

Wrist timing against atomic time

Log your watch against time.apple.com each morning to see how it runs over several days.

Six-position test

The app tells you when to turn the watch and reports average, spread and chronometer range.

Calibre table with sources

Beat rate and lift angle for common calibres, showing where each value comes from.

CSV export

Take every reading and time log into a spreadsheet. Always free.

iCloud sync

Keep watches and history on your iPhones and iPads through your own iCloud.

One watch page: on the wrist +3.1 seconds a day over 6 days, rate chart and timeline
Six-position report: average +2.6 seconds a day, spread 5.8, within chronometer range

Pricing

Free

$0

  • Unlimited measuring
  • One watch
  • Last 10 readings
  • Time logs
  • CSV export

Pro

$9.99 once

  • Unlimited watches and history
  • Six-position reports and PDF
  • Precision runs
  • Charts and comparison
  • iCloud sync
  • Widgets
  • Reminders

No trial. No subscription.