Justin Tadlock

X3P0: Progress is a block that allows users to create progress bars using a straightforward interface.
The block lets you add progress for nearly any type of goal:
<ul>
<li>Percentage: Outputs a percentage from 0% to 100%.</li>
<li>Decimal: Outputs a plain decimal number.</li>
<li>Currency: Create financial progress bars, choosing from a list of worldwide currencies.</li>
<li>Unit: Choose from a complete list of browser-supported units, such as yards, feet, liters, millimeters, and much more.</li>
</ul>
The output of the progress bar is highly customizable. Aside from standard block options, such as spacing, alignment, and border control, users also have a range of design tools at their disposal.
This block outputs proper <code><progress></code> and <code><label></code> elements in the markup. This should aid in accessibility, ensuring that all potential visitors to your site can read what the value of the progress is.

Progress Bar Block

A customizable progress bar block to visually track completion toward any percentage, numeric, financial, or unit-based goal.

Joeri van Veen

The reading progress bar is a great user experience on longreads. Especially if it accurately depicts the reading progress in the article text, and nothing else. This is standard on single blog posts and enabled by default.
Customization:
<ul>
<li>
Location top of screen, bottom of screen or below a sticky menu.
</li>
<li>
Choose color of the reading progress bar.
</li>
<li>
Have the bar start at 0% even when part of the article is visible.
</li>
<li>
Select post types you wish the bar to appear, or individual posts.
</li>
</ul>
Behaviour:
<ul>
<li>
The reading progress bar has smooth initializing since part of the text may already be visible, after that a lightweight update-function ensures quick response while scrolling.
</li>
<li>
The bar can attach itself to any (sticky) element that you define as an admin, when there are multiple, the first visible element will be used.
</li>
<li>
When there is no (longer a) visible element to attach to, the bar displays at the top.
</li>
<li>
If there is no single article identified (by class names or id) it uses the whole page to calculate progress.
</li>
</ul>
Estimated reading time (beta)
Since 1.6.0 this plugin has rudimentary estimated reading time functionality, for when your theme does not support it out of the box. 
There are some potential issues, some of which cannot be fixed in a plugin. If it does not work for you, switch it off. It will have no effect on the plugin then.
This is my 6th WordPress plugin but my first one freely available to everybody. I hope you enjoy using it as much as I enjoy building it!
Regards, 
Joeri

WP Reading Progress

Light weight fully customizable reading progress bar. Sticks to top, bottom or sticky menu, with fallback for small screens. Includes ert (beta).

Progress Bar Block vs WP Reading Progress