You can look in your owner's manual for the specific model and watch battery size. Other methods include doing a quick google search with the brand name and model number or opening up the watch to read the number on the battery. 116 and 377 are common watch battery types to look out for.
What is a 364 battery?
Used in watches, toys, glucose monitors and calculators. Long Lasting Zero Mercury Specialty Battery. Cell size: 364. Replacement for: SR60, SR621SW, 280-34, D364, SB-AG, SB-DG, TR621SW.