The short answer
Canvas shows two grades (current and total) and has a built-in what-if simulator. PowerSchool shows one grade per course per term, has no student what-if, and treats Missing as a flag rather than a defined rule. PowerSchool is the system of record — its stored grades feed transcripts and GPA. Canvas is a course gradebook.
One grade vs two grades
Canvas shows a current grade (graded work only) and a total grade (ungraded work as zero), and students can toggle between them. PowerSchool's portal shows the teacher's calculated grade for the term — a single number per course per term. Whether ungraded work counts in PowerSchool depends on the teacher's setup (missing flags, zeros entered, publish settings), not on a student-facing toggle. If you look for a “total grade” in PowerSchool, you won't find one — the single number is the grade.
What-if: built in vs missing
Canvas has a built-in What-If feature: type a hypothetical score and the grade recalculates. PowerSchool's portal has no student-facing hypothetical-score simulator. The gap is real enough that third-party tools exist to add Canvas-style what-if to PowerSchool. Use the PowerSchool Grade Calculator's target solver for the same job.
Missing work: flag vs rule
In Canvas, a missing assignment is a status with a defined effect — it counts as zero unless excused, and Canvas can apply the status automatically. In PowerSchool, Missing is a flag with no universal calculation rule; districts often have teachers enter a 0 placeholder alongside the code. In Canvas, check the status. In PowerSchool, check the Score column — a 0 there counts; a bare flag with no score may not.
Configuration: per course vs cascade
Canvas weighting is set per course in Canvas. PowerSchool's method, weights, scale, and policies cascade district → school → course → teacher. In PowerSchool, more of the setup is decided above the teacher — which is why “how does PowerSchool calculate grades” has no single answer, and why two districts' PowerSchool setups can behave differently.
System of record
PowerSchool stores final grades that feed transcripts and GPA. Canvas is a course gradebook. That is why PowerSchool's GPA is computed from stored grades, and why a grade change in Canvas (a course tool) and a grade change in PowerSchool (the record) carry different weight.
Which calculator do I use?
Use the PowerSchool Grade Calculator for PowerSchool courses (method + statuses + floor + override) and the Canvas Grade Calculator for Canvas courses (groups + weights + drop rules + excused/blank/zero + current vs final). The methods, statuses, and portal behaviour differ too much for one calculator to serve both faithfully.
More: How to Calculate Your Grade in PowerSchool, How to Calculate Your Grade in Canvas, How to Calculate GPA in PowerSchool.