There is no specific size for the fish finder that can be termed as the right size, as there are many other factors affecting the same. The available sizes of the screen range from 3.5 inches to 19 inches.nnYou may opt for the biggest screen size that suits your budget to view more information on the screen at a single glance.nnIf your budget doesn’t permit, then try and find a mid-size screen of about 9 inches to enjoy benefits of bigger screen in your budget. However, if you want it to be handy, then go for the screen size smaller than 5”.