What does Water Resistence (ATM) meant for watches?

February 08, 2019

  • Waterproof 30 meters (3 ATM) for anti-washing hand splash;
  • Waterproof 100 meters (10 ATM) for snorkeling or swimming;
  • Waterproof 200 meters (20 ATM) for scuba diving.

These instructions seem clear, but blurred, just like the depth of scuba diving is only 30 meters, why do you need a watch with a waterproof depth of 200 meters? Since the waterproof is up to 30 meters, why can't I take a bath with a watch? How to interpret the meaning of it is a complicated question!


When the depth of the water increases by 10 meters, it will increase the pressure equivalent to one atmosphere. According to this principle, the general watch factory uses the pressure gauge to test the waterproof performance of the watch, so some watch manufacturers will mark the compression value ( Bar or atm) to indicate its waterproof value. 1bar is equal to 1 kilogram per 1 square centimeter, so the pressure of 10bar is equivalent to the pressure that can withstand the depth of 100 meters below the water surface, that is, waterproof 100 meters, 20bar is equivalent to waterproof 200 meters, and so on. If the watch has only Water Resistance and no numerical indication, it is 20 meters waterproof according to international standards.


However, the so-called stress test is static. When the watch is worn between the wrist or swimming, the pressure is dynamic. Therefore, the instantaneous pressure required by the watch is much greater than that of static, so it must be multiplied. The safety factor is doubled to ensure the waterproof performance of the watch, which is why the depth of the watch is much higher than the actual use.

Waterproof Level

(1) SWEAT-RESISTANT: It is very easy to understand, just to prevent sweat from running into the watch;

(2) WATER-RESISTANT: It is okay to occasionally touch the water. For example, if you water the flowers and accidentally spray it on your hands, don't be nervous, pick it up and wipe it clean. No problem. In short, it is to prevent it. Occasional small splashes in life;

(3) 30 meters waterproof (30M, 3ATM, 3BAR): The watch has the word "30M" on the watch. This is the waterproof watch.

(4) 50 meters waterproof (50M, 5ATM, 5BAR): The watch with the word "50M" on the watch, that is, the 50m waterproof watch, is the waterproof watch in the mind of consumers, which can be used for swimming and general housekeeping waterproofing. Watch, remember not to adjust the watch in the water.

(5) Diving watch (100 meters waterproof, 200 meters waterproof, 300 meters waterproof, etc.): It is a professional waterproof watch that can be used for underwater work such as swimming and diving.

The easiest way to distinguish the waterproof performance of a watch is to judge by shape: in general, the circular watch is the best waterproof, followed by the oval watch. The waterproof of the square or irregular watch is the worst, because The waterproof apron and the round are the closest. Secondly, the material also has a relationship. Copper, aluminum or gold-plated materials will deteriorate for a long time, which will affect the waterproofness. In addition, the crown, the back cover and the edge of the glass are the main places for water intake, so the design of the watch itself has a big influence, for example, a screw-in crown and a rear bottom cover and a bezel design are better. Thick models usually have better waterproof function; ultra-thin watches are not waterproof enough due to limited space, so the waterproofness is poor; and the multi-function design is easy to be leaky. The waterproof watch may have fog in areas with large temperature differences.

In addition to its own design factors, improper use is the main culprit in the water intake of the watch. For example, after adjusting the time, the faucet is not tightened; the watch is prone to fogging under the condition of high temperature and low temperature; in addition, wearing a watch to take a bath, There may be no problems at first, and after a while, the watch will definitely have problems. When the watch encounters the problem of water ingress, it is best to send it to the watch store or drying by the professional. It is best not to blow it dry by the hair dryer when the machine is not taken out. This move not only does not help, but it is easy to leave the evaporated moisture inside the movement. 

Usually, most brands of diving watches are only 1 year waterproof, so regular testing is very important. In addition, although the international organization ISO has strict regulations and tests on the waterproof label of the diving watch, since the specifications of the waterproof label are not consistent in each country, we may wish to distinguish the waterproof label of the watch if it is impossible to distinguish whether it is in conformity with the regulations. 

Leave a comment