The Reading Progress plugin for WordPress is flexible and easily customizable, allowing you to change parameters without diving into the code.
Style: Default, Rounded, Plastic, Animated, Shine, Glow
Color: Select color or gradient for Progress Bar.
Shadow: Customize shadow for a progress bar.
Height: Select height in pixels for Progress Bar.
Position: Select position where to show Progress Bar. Top or Bottom.
Offset: Distance to move progress bar up or down, depending on the selected position.
Custom Selector: Enter a valid CSS selector to display the progress bar not for the entire page height, but for a specific part. Leave blank to use full page height.