What is "good" and "bad" accuracy? ~ Mainspring Q&A ~ Answering your watch questions ~

Q: What does it mean if a watch has good or bad accuracy?

If a watch's gain or loss is small compared to the actual time, it is said to have good accuracy. If it is large, it is said to have poor accuracy. The accuracy of a watch when actually worn on the wrist is called "dynamic accuracy (portable accuracy)," while the accuracy when the watch is not moving is called "static accuracy."

A: If the difference between the displayed time and the actual time is small, it's "good." If it's large, it's "bad."

The word "accuracy" is often discussed among watch enthusiasts. Strictly speaking, there are various standards, but when watch enthusiasts and the media talk about accuracy, they are basically referring to the accuracy of the watch when worn on the wrist (dynamic accuracy, portable accuracy). Good accuracy means that the watch loses or gains little, while poor accuracy means that the watch loses or gains a lot.

The Swiss chronometer standard specifies the accuracy of a watch. The standard set by the chronometer standard is that the time must be within -4 to +6 seconds per day. Omega, Patek Philippe, Grand Seiko, Rolex, and other brands also now state their accuracy standards.

Good static accuracy does not necessarily mean good dynamic accuracy

However, the accuracy that each manufacturer states is only the accuracy when the watch is not moving (static accuracy). Therefore, when you wear the watch on your wrist and shake your arm or subject it to impact, the actual accuracy (dynamic accuracy) can change significantly. It is generally said that watches with low vibration frequencies and small balance wheels are more likely to have a gap between static accuracy and dynamic accuracy, while watches with high vibration frequencies and large balance wheels have a smaller gap between the two. Currently, many watch manufacturers are working on developments to narrow the gap between static accuracy and dynamic accuracy.

Even if there is a large discrepancy between static and dynamic accuracy, it is possible to narrow the gap through adjustment. In that case, be sure to properly communicate to the watchmaker the conditions under which the watch is being used. Also, by changing the orientation of the watch when it is stored, you can adjust the speed of the watch (see the reference article below for adjustment methods).