Estimate time to make up missed assignments.
Catching up is only meaningful alongside ongoing work, because new assignments keep arriving. Dividing the missed work across the available days gives the extra daily load, and adding your normal daily coursework gives the figure that actually determines whether the plan is possible. Once the total passes about eight hours a day, requesting an extension is a better strategy than attempting it.
Catch-up load
Catch-up hours = assignments missed x hours per assignment; extra per day = catch-up hours / days available
Total daily load
Total daily workload = ongoing daily coursework + extra hours per day
Usually current work first where late penalties on missed items are already fixed, since falling behind again compounds the problem. Weight by marks at stake.
As soon as the arithmetic shows the plan is not feasible, not after missing another deadline. Requests made early with a plan attached are treated far more favourably.