How weighted grades work, with examples

What is a weighted grade?

A weighted grade is an average where some items count more than others. Instead of treating every assignment equally, your teacher gives each category a share of the final grade. A course might split it like this:

• Homework: 20%
• Quizzes: 15%
• Midterm exam: 25%
• Final exam: 40%

“Your final grade is made up of homework (20%), quizzes (15%), the midterm (25%) and the final exam (40%).”

Example course syllabus

Your syllabus is the place to look for these numbers. They tell you how much each result can move your grade: 10 more points on a final worth 40% adds 4 points to the course, while 10 more points on quizzes worth 15% adds 1.5.

How to calculate a weighted grade

1. Write down each grade as a percentage.
2. Multiply each grade by its weight.
3. Add up the results.
4. Divide by the sum of the weights.

Here is one student’s course, using the weights above:

Dividing the total by the sum of the weights gives 8,585 ÷ 100 = 85.85, or 85.9% rounded to one decimal place.

When weights change the answer

In that example, a plain average of the four grades is 85.75%, very close to the weighted result. That’s only because the grades are close together.

Weights matter most when your results are far apart. With homework at 100% (worth 20%) and a final at 60% (worth 80%), a plain average says 80%. The weighted grade is (100 × 20 + 60 × 80) ÷ 100 = 68%. That’s the difference between a B and a D on the most common US scale.

If you don’t have all your grades yet

During a term, your weights won’t add up to 100% yet. Divide by the weights you have so far, and the result is your average on the work graded so far.

Say you only have homework at 92% (worth 20%) and quizzes at 85% (worth 15%):

1. Multiply and add: 92 × 20 + 85 × 15 = 3,115.
2. Add the weights: 20 + 15 = 35.
3. Divide: 3,115 ÷ 35 = 89.

You’re at 89% on the 35% of the course graded so far. Dividing by 100 instead would give 31.15%, which makes it look like you’re failing when you aren’t.

Categories with several items

A category often holds many items, like ten homework assignments that together are worth 20%. Average them first, then use that average as one grade with the category’s full weight.

If your teacher drops your lowest score, leave it out before you average, and keep the category’s weight the same. Quiz scores of 60, 80, 90 and 100 with the lowest dropped average (80 + 90 + 100) ÷ 3 = 90.

Points and percentages

Some courses have no categories, only total points. Divide your points earned by the points possible, and you don’t need weights. Averaging percentages gives a different answer, because small assignments count too much that way. A quiz at 8 out of 10 and an exam at 90 out of 100 average to 85% as percentages, but 98 out of 110 points is 89.1%.

Check which of the two your course uses. Your syllabus or your teacher can tell you.

Common mistakes

• Leaving out the weights. A small quiz ends up counting as much as the final exam.
• Dividing by 100 too early. If your weights add up to less than 100%, divide by their sum.
• Mixing points and percentages. Turn each item into a percentage first: 42 out of 50 is 84%.
• Adding a category item by item. Ten homework scores at their own weights give each one the full 20%. Average them first.
• Treating your own result as official. Schools can round differently or count only some work, so your teacher’s or school’s figure is the one that counts.