100% View is not accurate after export

Read carefully the answers by thedigitaldog and D Fosse

If you want the image to appear onscreen at the size it will be printed, do not use 100% zoom. Use View -Print Size and ensure that the screen resolution is set as per thedigitaldog 's description above.

Dave

You have a high-resolution screen. That has some implications.

In Photoshop, 100% has nothing to do with physical size. It means one image pixel is represented by exactly one screen pixel. This is the only absolutely accurate way to view the full pixel data. But it also means that on a high-density screen, the image will be very small compared to a traditional screen.

Other consumer-oriented viewers don't need to display accurately. To those applications, it's expected that they show the image at roughly the same size across all screens. So when these applications detect a high-density screen, they scale up. They use four screen pixels to display one image pixel.

Its a good idea to find out what the true, native resolution of your display is (they are NOT all 72PPI!).
Measure the width of your display and divide that by the number of pixels its displaying.
For example,on my NEC PA271Q, the width is 23.5 inches. Its resolution is 2560x1440. 2560/23.5=109PPI.

This must be entered into the PS preferences as seen below for PS to work correctly using "View>Print Size".