Grade calculator

Add one row per category. Give it a weight and either a single percentage or a list of scores written as points earned out of points possible. You can leave a category empty if nothing in it has been graded yet.

How the weighted average works

Each category's percentage is multiplied by its weight, and the results are added up. The total is divided by the sum of the weights, so the answer is still a percentage if your weights add to 80 or 120 instead of exactly 100.

For a category with several scores there are two reasonable ways to get its percentage.

Pooled points add up everything you earned and everything that was possible, then divide. This is how a gradebook behaves when the category is worth "total points".

Mean of percentages works out each assignment's percentage first and averages them. Every assignment counts equally regardless of how many points it was worth.

The two methods agree when every assignment is worth the same number of points. They drift apart when point values differ. The calculator defaults to pooled points and lets you switch. We could not find a source that says which method most schools use, so check how your teacher's gradebook behaves.

Worked example: a simple split

Homework 20% at 92, quizzes 20% at 85, tests 40% at 78, final project 20% at 88.

• Homework: 0.20 x 92 = 18.4
• Quizzes: 0.20 x 85 = 17.0
• Tests: 0.40 x 78 = 31.2
• Project: 0.20 x 88 = 17.6

The total is 84.2, so the class grade is 84.2%. On a scale where 83 to 86 is a B, that is a B.

Worked example: pooled versus mean

Homework is worth 25%, tests 50% and participation 25%. Homework scores are 8 out of 10 and 45 out of 50. The test is 168 out of 200, and participation is 10 out of 10.

Pooled, homework is 53 out of 60, which is 88.33%. The grade is 0.25 x 88.33 + 0.50 x 84 + 0.25 x 100 = 89.08.

By mean of percentages, homework is the average of 80% and 90%, which is 85%. The grade is 21.25 + 42 + 25 = 88.25.

A difference of 0.83 points looks small, but if your A starts at 89 it is the whole question. One short quiz you did badly on weighs much more in the mean method than in the pooled one.

Empty categories

Say homework is 30% at 90, labs 20% at 80, participation 10% at 100, and the exam (40%) has not happened yet.

Treat the exam as not yet counted and rescale the remaining 60% of weight: (27 + 16 + 10) / 60 = 88.33%. That is your grade so far.

Treat the empty exam as a zero and the same numbers give 53 out of 100, or 53%. That is the worst case if you skipped it.

Both are right for different questions. Some online gradebooks show one and some the other, which is why a grade can look much lower in the portal than on your own spreadsheet. The calculator has a switch for each. If you want to plan for the exam itself, the final grade calculator turns the rest into a target score.

Why schools differ

Weights, not just scores, change from school to school. Broward County gives each quarter 37.5% and the semester exam 25%. Cab Calloway School of the Arts in Delaware weights its four quarters at 2 each and its two exams at 1 each, so each quarter is a fifth of the course and each exam a tenth. Your teacher's own plan for the class is the one to use.

Letter cutoffs differ too. Green Bay's public schools use 93 for an A and 90 for an A-. North Carolina's state scale, reproduced by a county school system, has 90 as the A line with no minus. Whichever you choose in the calculator, it only affects the letter, not the percentage.

How colleges use the result

Colleges mostly see the letter that your class percentage became, not the percentage. How much the letter matters depends on the college. The University of California counts A as 4, B as 3, and says pluses and minuses do not count. The University of Michigan treats A+, A and A- all as 4.0. So if your school's A- begins at 90, an 89.6 and a 90.0 can differ by a whole grade point on those colleges' GPA, even though the real gap is under half a point.

That is a reason to know your school's exact cutoffs and rounding rule, and to ask a teacher early rather than at the end of the term.

Common mistakes

• Adding weights and scores together without multiplying.
• Entering a weight as 0.2 in one row and 20 in another.
• Putting the same assignment in two categories.
• Forgetting that dropped lowest scores can change a category's percentage.
• Counting a category the teacher has not started grading. Leave it empty.

The cutoffs the calculator can use

The letter next to your percentage comes from the scale chosen in the settings. A percentage belongs to the highest letter whose cutoff it reaches, with no rounding, so an 89.6 stays below a 90 line. Published cutoffs differ: