Chronometer Accuracy Calculator
Calculate watch accuracy, daily drift, and cumulative error. Check if your watch meets COSC chronometer standards.
COSC Accuracy Check
Enter your watch's measured drift to check against COSC and other certification standards.
Daily Drift Calculator
Calculate daily drift from a measured time difference over any period.
Accuracy Over Time
Project cumulative drift over weeks, months, and years.
Formula
Frequently Asked Questions
What is COSC chronometer accuracy?
How accurate should a luxury watch be?
How do I measure my watch's accuracy?
Understanding Watch Accuracy
Accuracy is one of the most important performance metrics for any mechanical watch. While quartz watches achieve exceptional precision through electronic oscillation, mechanical watches rely on the balance wheel and hairspring, making their accuracy a testament to engineering excellence.
Accuracy Standards Compared
COSC Chronometer: The industry standard, requiring -4/+6 seconds per day. Approximately 1.75 million movements are certified annually.
Rolex Superlative Chronometer: A stricter in-house standard of -2/+2 seconds per day, tested after casing (not just the movement).
METAS Master Chronometer (Omega): Tests for accuracy (0/+5 sec/day), magnetic resistance (15,000 gauss), water resistance, and power reserve. The most comprehensive certification available.
Grand Seiko Special Standards: GS mechanical watches target -3/+5 seconds per day, while Spring Drive achieves an remarkable +/-1 second per day.