How your class grade is worked out
In weighted mode the calculator adds up the points you earned in each category and divides by the points possible in that category. That gives one percent per category. Each percent is then multiplied by the category's weight, and the results are added together.
Category percent = points earned ÷ points possible × 100
Class grade = Σ (category percent × weight) ÷ Σ weights that have grades
In total points mode there are no categories: your grade is every point you earned divided by every point possible. Bigger assignments count for more simply because they are worth more points.
Worked example
A class weights homework 20%, quizzes 30% and tests 50%. You have two homework sets, 18 out of 20 and 9 out of 10, a quiz at 42 out of 50 and a test at 88 out of 100.
- Homework: (18 + 9) ÷ (20 + 10) = 27 ÷ 30 = 90%
- Quizzes: 42 ÷ 50 = 84%
- Tests: 88 ÷ 100 = 88%
- Class grade: 0.20 × 90 + 0.30 × 84 + 0.50 × 88 = 18 + 25.2 + 44 = 87.2%, a B+
The next letter up is an A- at 90%, which is 2.8 percentage points away. Before the test, the grade would have been (0.20 × 90 + 0.30 × 84) ÷ 0.50 = 43.2 ÷ 0.50 = 86.4%, because homework and quizzes were the only work graded. These numbers are loaded when the page opens.
Switch the same scores to total points and you get 157 ÷ 180 = 87.2% again, but only by coincidence: drop the test and it becomes 69 ÷ 80 = 86.25%.
Missing categories and weights that do not add up
If a category has a weight but nothing graded yet, it is left out and the remaining weights are scaled so they fill 100%. The calculator tells you when it has done this and how much each category counts for right now. If your weights add up to something other than 100, the same scaling applies, so weights of 1, 1 and 2 work just like 25%, 25% and 50%.
The letter grade scale
The default cutoffs are a common US plus and minus scale:
| Letter | Percent | Letter | Percent |
|---|---|---|---|
| A | 93 to 100 | C+ | 77 to 79 |
| A- | 90 to 92 | C | 73 to 76 |
| B+ | 87 to 89 | C- | 70 to 72 |
| B | 83 to 86 | D+ | 67 to 69 |
| B- | 80 to 82 | D | 63 to 66 |
| D- | 60 to 62 | ||
| F | below 60 |
Scales really do differ. The College Board's BigFuture guide to the 4.0 scale shows a plain chart with A at 90 to 100 and notes that some schools do not use pluses and minuses and others have different cutoffs. Type your own school's cutoffs into the table and they are saved with your rows.
Rounding
Percents are shown to one decimal, rounding a 5 up, and the letter comes from that shown number. So 89.95% shows as 90.0% and counts as an A-, while 89.94% shows as 89.9% and is a B+. The calculator also strips the tiny binary errors computers make with decimals, so a score that should come out at exactly 90 is never shown as 89.9.
Limits
- Your teacher's gradebook and your school's policy win. Some teachers average assignment percents instead of pooling points, drop the lowest score, or count missing work as zero.
- Ungraded rows (no score and no maximum) are ignored rather than counted as zero.
- Want to know what you need on the exam? Use the final grade calculator with the percent from here.
Questions people ask
How do I calculate a weighted grade?
Work out your percent in each category first, then multiply each one by its weight and add them up. With homework at 90% (weight 20%), quizzes at 84% (30%) and tests at 88% (50%), the grade is 0.20 × 90 + 0.30 × 84 + 0.50 × 88 = 18 + 25.2 + 44 = 87.2%. This calculator does that for you as you type.
What if a category has no grades yet?
The calculator leaves it out and scales up the other weights so they still add up to 100%. If tests are worth 50% and you have not taken one, homework (20%) and quizzes (30%) count as 40% and 60% of your grade for now. Many online gradebooks do the same thing, but ask your teacher, because some count missing work as zero instead.
Why does 89.95% show as an A-?
The calculator shows your percent rounded to one decimal, rounding a 5 up, so 89.95% shows as 90.0%. The letter is then taken from that shown number, so what you see and the letter always agree. Your school may round differently or not at all, and a teacher who does not round would call 89.95% a B+.
Should I use weighted categories or total points?
Use whichever your syllabus describes. If it lists percentages for categories such as homework, quizzes and tests, pick weighted categories. If every assignment is simply worth a number of points and your grade is points earned over points possible, pick total points. The two can give different answers for the same scores.
Can I change the letter grade cutoffs?
Yes. Open "Letter grade cutoffs" and type the lowest percent for each letter. The default is a common US scale with A at 93 and above, A- at 90 to under 93, and F below 60. Many schools use a plain 10-point scale (A from 90) instead, so copy the one in your syllabus.
Does extra credit work?
Yes. Enter a score above the points possible, such as 105 out of 100, and it counts. A separate extra credit assignment worth 5 points with 0 points possible cannot be entered, because a maximum of zero has no percent. Add those points to the assignment they belong to instead.