Is your watch running fast or slow? Enter how many seconds it has drifted over a few days and this calculator gives the seconds-per-day rate plus a verdict against the real standards: COSC chronometer is -4/+6, and a normal automatic sits around -10 to +20 a day.
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Frequently asked
What is a good accuracy for a mechanical watch?
A typical modern automatic runs about -10 to +20 seconds per day. COSC chronometer certification requires -4/+6, and Omega’s METAS Master Chronometer standard is 0/+5. Anything within a few seconds a day is excellent for a non-certified movement.
How do I measure my watch’s accuracy?
Set it precisely against an atomic clock or your phone, wait several days while wearing it normally, then compare again. Divide the total drift in seconds by the number of days to get seconds per day. Measure over several days for a reliable figure.
Is +8 seconds a day good?
Yes. +8 seconds a day is well within normal range for a mechanical watch and many enthusiasts are happy with it. It is outside COSC (-4/+6) but most non-chronometer movements are not expected to hit that.
Why does my watch accuracy change?
Rate varies with how wound it is, position (dial up vs crown down overnight), temperature, and magnetism. Resting the watch in a different position overnight is a common trick to nudge the daily rate up or down.
Daniel Hart is the editor of Watch The Watch. He researches and writes the site’s buying guides, brand comparisons, and explainers, focused on accessible, enthusiast-level watches — affordable automatics, divers, field and dress watches, everyday quartz, and the straps, winders and tools that go with them. The goal is practical, budget-aware advice that helps readers choose the right watch for their wrist and their budget. Recommendations draw on manufacturer specifications and the wider enthusiast community.