Tumblr allows you to customize the look of your chosen theme extensively, including both the size and appearance of the fonts used on your page. You can use the site's “Customize” window to edit the Cascading Style Sheets that control your page's appearance. Alternatively, the Dashboard's HTML view lets you control the appearance of individual posts by inserting HTML tags directly into your content.

HTML View

The HTML view is part of the post creation window of the Tumblr dashboard. When selected, it display the HTML tags that make up blog posts as well as the posts' content. The HTML view also allows you to edit a given post's HTML tags, allowing you to change the properties of a small portion of your text. The HTML view is useful if you only want to change the size of part of your blog post. For example, you might use it to make a single word larger.

Editing in HTML View

To access the HTML view, first click the “gear” icon on the post you wish to edit. Select “Edit” and then click “HTML.” Tumblr supports two tags for making text larger or smaller: the <big> tag and the <small> tag. To make a portion of your text bigger, type “<big>” (without quotes here and throughout) directly before the start of the text and then type “</big>" directly after the end of the text. The “<small>” tag works in the same way, but makes text smaller instead. Click “Save” when you have finished editing.

The Customize Page

The Customize page allows you to edit the HTML and CSS that powers your blog itself as opposed to editing the HTML of an individual post. Using the Customize page gives you a great deal of control over the ways that fonts display on your page, allowing you to specify a size for your text. It is best to use the Customize window if you want to change the size of all the text on your page, as edits made on this page usually apply to your whole blog.

Using the Customize Page

To open the Customize page, click the “Customize” link on the main page of the Dashboard. Next, click “Edit HTML” to access the code behind your page. Press “Ctrl-F” to bring up a Find box and search for “font-size”. This will help you to locate the area of code that deals with fonts in your theme. Change the “font-size” variable to the size you want. For example, if your text was 10 points but you wanted to change that value to 12, you would change the line “font-size: 10px” to “font-size: 12px”.