Right now, there is not a direct way for an automatic calculation of estimated completion time on a module. For example, a simple canvas page giving students instructions to navigate to their text and read the assigned chapter(s) will be detected as a quick read, even though it is instructions for what could be a long assignment. For this to be calculated correctly, there would have to be a blank for teachers to fill with the expected completion time for each activity they schedule. Teachers who wish to do so, can do this today on a canvas page inserted at the beginning of each module and also list the module objectives and activities on that page.
An automated version would be interesting, because it would allow those completion times to display in the syllabus and calendar, so that students have a "start before" time. In fact, on the calendar, the "start before" times could stack so that multiple activities from multiple courses with the same due time would not also have the same start time. Of course, that would also require the calendar and syllabus to display activities posted within a course in the same order as they are displayed in the module, which is not what happens right now. (Activities with the same due time seem to be displayed with those that require a submission in the fist group, and those that don't in the second group, with each group in alphabetical order.)
For now, the best source for an estimated completion time is going to be the instructor of the course, but you might want to add an idea for improving the canvas syllabus here: https://community.canvaslms.com/t5/Idea-Conversations/idb-p/ideas