Step 1: Open a book in your Amazon kindle and tap the top of your screen.
Step 2: Select the “Aa” graphic, which is the text size key. This graphic will help you both change your font size and the font itself.
Step 3: Adjust to the size you desire. On the standard Kindle, you can choose from six different font sizes.
Step 4: On a Kindle PaperWhite, you can change your font size simply by sliding your thumb and forefinger away from each other while placed on the screen. It’s similar to how you would zoom in and out on a smartphone.