This question does not have a solid answer because Presentations are responsive. When a page is uploaded to MoxiPresent the size of the page will be changed to fit the screen it is viewed on. 

The base width of a Presentation page is 1200px. The page size changes if the screen that the page is being viewed on is:

• larger, we add margins to the left and right
• smaller, the page shrinks to fit the width of the screen