Compare two readings
Check whether two rate estimates agree using both measurements’ stated uncertainty.
Open the free repeatability calculatorKapella
Measure a mechanical watch with evidence.
Hairspring is an iPhone timegrapher that reports rate, beat error, an honest amplitude range, and whether two readings agree after accounting for uncertainty.
Track accuracy over time
Convert a clock difference and elapsed time into seconds per day, entirely in your browser.
Open the watch accuracy calculatorRead a timegrapher
Interpret rate, trace shape, beat error, amplitude, and repeatability in the right order.
Read the practical guideChoose browser or app
Compare a zero-install browser check with a native iPhone workflow and a dedicated bench machine.
Read the browser vs app guideInspect the method
Review the app’s measurement boundaries, privacy posture, screenshots, and press notes.
See method and press notes