Work out watch accuracy deviation instantly with clear inputs, formula shown and shareable results.
Daily rate is the total deviation divided by the days observed, then scaled to a month and a year for comparison against manufacturer specifications. COSC chronometer certification allows minus four to plus six seconds a day, so a watch gaining two seconds daily is performing better than most.
Daily rate
seconds per day = total deviation / days observed
seconds per day = total deviation / days observed. Daily rate is the total deviation divided by the days observed, then scaled to a month and a year for comparison against manufacturer specifications.
COSC chronometer certification allows minus four to plus six seconds a day, so a watch gaining two seconds daily is performing better than most.
Enter total deviation observed, days observed. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.