As you probably already know, the Apple Watch comes in two sizes: 42mm and the 38mm which is slightly smaller. Unfortunately, Apple didn’t provide the exact size for each watch. According to an article from David Pogue in yahoo.com tech category, the Apple watch 32mm has a 1.7-inch screen and the 38mm has a 1.5-inch screen.
I did made my measurement using an official image while taking the Apple Watch case height into consideration while measuring the screen size using the ruler in Adobe Photoshop, and I’ve got a similar results. So I can assume that the numbers mentioned in that article are correct. I also assume that David asked that question to one of Apple’s representatives to get a correct answer.
That’s obviously a tiny screen and you can’t compare it with a small smartphone display, but that’s a watch, not a smartphone. Yet, Apple worked hard to make the interaction with the phone as easy and user-friendly as possible using a, what Apple calls “The Digital Crown” and a responsive touchscreen that recognizes pressure and the Haptic Feedback system.
source: yahoo.com