Start with the syllabus
A course can use assessment categories or a pool of points. These are different weighting systems. Before combining marks, find out which one your instructor uses.
A points-based course
Suppose you earn 18/20 on a quiz and 70/100 on an exam. Pooling the points gives 88/120 = 73.33%. The exam matters more because more points were available. Use the percentage calculator with the combined points.
A category-weighted course
Now suppose quizzes are worth 40% and the exam is worth 60%. The quiz percentage is 90%, so the course grade is 90 × 0.40 + 70 × 0.60 = 78%. The same marks give a different result because the syllabus assigns different importance. Use the weighted grade calculator.
Why averaging percentages can go wrong
The simple average of 90% and 70% is 80%. That is correct only if both assessments have equal weight. It is neither the points-based result nor the 40/60 category result above.
Incomplete work is not always a zero
If only the 90% quiz category has been completed, your normalized current average is 90%. Its contribution to the full course is 36 percentage points. Treating the ungraded exam as zero would produce 36%, which answers a different question. Check whether your online gradebook includes ungraded assessments before using its current percentage.
Categories with multiple assignments
Calculate each category’s own average first, using the instructor’s rules. Then apply category weights to those category averages. Do not apply the entire category weight separately to each assignment. Dropped scores and extra credit can change the category average.