Most instructors find that even with scanning, Gradescope saves them 30-60% time compared to grading on paper. Once you’ve done the scanning process once, the subsequent scans will go much more quickly. Ultimately, scanning into Gradescope eliminates the administrative work of tallying scores altogether.
In addition to grading being much faster, you don’t have to spend time in class returning work, or time in office hours on regrade requests. With scanning you also avoid students cheating by changing their answers after they get their work back.