1. From the history of watches

The concept of watches first emerged in the 19th century. At that time, watches, strictly speaking, were called bracelet watches, precious metal designs intended as adornment for women. They were adorned with magnificent gems and the watch face was concealed by a cover, making them more like an expensive bracelet with an added time-telling function. For men at the time, pocket watches were their only timekeeping tools.

Until 1904, Alberto Santos-Dumont, a Brazilian aviator, found it inconvenient to check his pocket watch while flying. He commissioned the luxury brand Cartier to custom-make a portable watch that could be worn on his wrist, for the convenience of pioneering pilots like himself. The watch Cartier customized for Santos was designed to be worn on his left wrist to leave his right hand free for controlling the aircraft's steering, assuming that Santos was right-handed. If he were left-handed, the watch would probably have been worn on the right wrist. This watch became the basic design model for wristwatches thereafter, known as the Santos, and went on sale after 1904.

2. From the perspective of watch design

Initially, watches were all mechanical, requiring winding and time adjustments. The watch's winding and time-setting knobs were all located on the right side of the watch face. Wearing it on the left wrist allows for convenient operation with the right hand. If worn on the right wrist, this would clearly be inconvenient. Though quartz watches now exist, many high-end watches remain mechanical. Therefore, for convenience, they should be worn on the left wrist.

Moreover, the vast majority of people are right-handed, using their right hand more frequently. Wearing a watch on the right hand would be very inconvenient and prone to damage, especially for mechanical watches. Mechanical watch components have six orientations. The amplitude will vary slightly when the watch is in different positions. Because the movement range of the right hand is significantly larger than the left hand, wearing a mechanical watch on the right hand would affect its timekeeping accuracy.

3. From a health perspective

In Traditional Chinese Medicine (TCM), there is a point on the wrist called "Cunkou" (寸口), connecting three important pulse points: Cun (寸), Guan (關), and Chi (尺). These three pulse points are closely related to a person's health, distributed on both wrists and below the thumb. TCM believes that these three pulse points in women are located on the right wrist; blood flows from the heart's capillaries to this area on the right hand. Prolonged pressure from a watch can affect the normal functioning of the heart. Therefore, women wearing watches on their left wrists is more consistent with medical and health theories, and is healthier.