Size of the screen in a smartphone.

I think the ideal size of a smartphone should be about 5.5 inch. But if you see the current models being launched, you will get all above 6 inch screen. In addition to the convenience in handling, mobile companies also want that watching videos on the mobile should be convenient and thus they go for bigger screen size.

I have used many sized handsets with different screen size. I have used a Samsung Wave phone with 4-inch size, Moto G with 4.5-inch size, Le Tv 1s with 5.5-inch size. The best working handset was 5-inch size screen handset i.e. Moto G. The screen is accessible by thumb from diagonal points with ease. It is now even difficult for me to touch an upper right corner of the screen by a left-hand thumb to my Honour 6x mobile.

Well I had used
1.Sony Xperia e dual which had 3.5 inch screen
2.Xiaomi mi 3 which had 5 inch screen
3.Xiaomi redmi 3s prime which had 5 inch screen
4.Iphone 6s which 4.7 inch screen
5.Xiaomi Poco f1 ( currently using ) which has 6.2 inch screen
I was comfortable with Iphone 6s and Xiaomi mi3 screen size
But you get to enjoy Poco f1 6.2 inch screen by using it for entertainment purpose.
In terms of usability, sometimes it cannot be used by one hand even after having big hand
Those who have small hands will struggle each and every time to use the upper part of the screen.
The ideal screen for everyone will be 5 inch screen I think.