As you know, CSS has several units like px, %, EM or REM for expressing a length and each of them is suitable for its conditions.
While you're creating your layout in Elementor, you may need to change the CSS units for the CSS properties that take length values.
In order to change the CSS length unit in Elementor follow the steps below:
1. In Elementor, select the element for which you want to change the CSS length unit, so that a new dashboard on the left will emerge with the element's settings.
2. In Style tab, any CSS properties that takes length values such as margin, padding, font-size , etc. has an option for changing the units. Select your preferable unit and type in the length value.
3. Change the settings and Update the page.
Note: If you want to learn about changing the units for CSS properties in Customizer, you can refer to this article.