Most of the people want a bigger font size to grab attention of their readers specially for the heading elements. Hence there is a need to change the font size. As you probably already know, you can quickly see there aren’t any apparent options for changing your text size. You can easily solve this issue by clicking on the “Toolbar Toggle” button, which is the second icon from the right under the “Add Media” button.
You’ll see a box on the left of the toolbar that by default will say “Paragraph”. Click anywhere on the box and a drop down menu will appear.

You will immediately notice that there are only eight options for your text size, which range from “Paragraph”, “Headings 1-6”, and “Preformatted”. These sizes are controlled by your theme’s stylesheet file (style.css) to make sure that the font size is coherent with everything. All you have to do is insert the text and choose a heading.

I’m sure most of you know this method so we’ll explain how you can select any font size you like from a drop down menu. This method utilizes a WordPress plugin known as TinyMCE advanced.

After activation only you have to do is to configure the editor settings. For this simply go to Settings » TinyMCE. Here you will see the TinyMCE Editor toolbar with used and unused buttons.

On this page you need to drag and drop the font size button from the unused buttons to any row in the toolbar. Do not forget to save changes.

To see the changes create a new post or edit an existing one and you will see the default WordPress visual editor is replaced by the TinyMCE Advanced editor with font-size button.

Now you can select any font size you like from the drop down. This gives you more freedom over things because now you can actually have font-size even smaller than the normal body font i.e 8pt or 10pt.

There is a downside of this method: if you ever change themes, you have to account for all the font size changes you made in individual posts.