Direct answer: To find the average of grades, add all the grades together and divide by how many there are — if every grade counts equally. For 75, 85, 90, and 80: (75 + 85 + 90 + 80) ÷ 4 = 330 ÷ 4 = 82.5%. If the grades have different weights, use a weighted average instead. And if the percentages come from groups of different sizes, average the underlying totals — not the percentages.
Grade averages are the single most common reason students search for “average.” The method is the same as any average — add and divide — but grades hide two traps that trip up even careful students: different weights, and percentages from different-sized groups. This guide works through all three cases with exact numbers. If you need the basics first, start with our guide on how to find the average.
Case 1: Grades That Count Equally
When every grade counts the same, the average is a plain arithmetic mean.
Example: Four test scores — 75, 85, 90, and 80.
Step 1 — Add: 75 + 85 + 90 + 80 = 330. (75 + 85 = 160; 160 + 90 = 250; 250 + 80 = 330.)
Step 2 — Count: 4 grades.
Step 3 — Divide: 330 ÷ 4 = 82.5%.
The average grade is 82.5%.
This is the case most students mean when they ask “what is my average?” — four quizzes, five homework scores, three test marks, all worth the same. The free how to calculate average tool at Calcrio does this in one click.
Case 2: The Average of Percentages
Averaging percentages works exactly the same way — when the percentages are equally weighted.
Example: Three test percentages — 80%, 90%, and 70%.
Step 1 — Add: 80 + 90 + 70 = 240.
Step 2 — Count: 3 values.
Step 3 — Divide: 240 ÷ 3 = 80%.
The average of 80%, 90%, and 70% is 80%.
The rule is simple: average percentage values directly only when they are equally weighted. The moment the percentages represent different numbers of observations, the rule breaks — and that is Case 3.
Case 3: The Trap — Percentages from Different-Sized Groups
This is the trap that catches almost everyone. Two groups:
- Group A: 90% — but out of 100 students (90 correct answers).
- Group B: 70% — but out of 10 students (7 correct answers).
The wrong way: (90 + 70) ÷ 2 = 80%. This treats the two percentages as equal — but Group A is ten times bigger than Group B.
The right way: combine the underlying totals.
- Correct answers: 90 + 7 = 97.
- Total students: 100 + 10 = 110.
- Combined percentage: 97 ÷ 110 = 0.8818…, about 88.18%.
The combined percentage is about 88.18%, not 80%. The bigger group dominates, and it should — 90 of the 97 correct answers came from Group A. Whenever percentages describe different sample sizes, use the underlying totals or a weighted average. The same logic applies to batting averages, survey results, and pass rates — anywhere a percentage hides a count.
A classroom version of the same trap: Class A averages 80% with 50 students, Class B averages 90% with 100 students. The simple mean of the two percentages is 85% — but the real combined average is (80 × 50 + 90 × 100) ÷ 150 = 13,000 ÷ 150 = 86.67%. From raw scores: (40 + 90) ÷ 150 = 86.67%. The bigger class pulls the answer toward its 90%.
Case 4: Grades with Different Weights
When grades have different weights — a final exam worth 40%, homework worth 20% — a plain average is the wrong tool. Use the weighted average:
| Category | Score | Weight | Contribution |
|---|---|---|---|
| Homework | 90% | 20% | 90 × 0.20 = 18 |
| Quizzes | 80% | 20% | 80 × 0.20 = 16 |
| Midterm | 85% | 25% | 85 × 0.25 = 21.25 |
| Final exam | 92% | 35% | 92 × 0.35 = 32.2 |
Add the contributions: 18 + 16 + 21.25 + 32.2 = 87.45.
Divide by the total weight: 0.20 + 0.20 + 0.25 + 0.35 = 1.00, so the weighted average is 87.45%.
The plain average of these four scores would be (90 + 80 + 85 + 92) ÷ 4 = 347 ÷ 4 = 86.75%. The weighted average is higher (87.45%) because the best score — the final exam at 92 — carried the biggest weight. Our full guide to weighted average explained works through this method step by step.
Grade Average vs GPA: What Is the Difference?
A grade average and a GPA are related but not the same thing:
| Grade average | GPA | |
|---|---|---|
| What it measures | The average of scores, usually as a percentage | Grade points on a scale (usually 0–4.0) |
| Weights | Equal, or by assignment weight | By credit hours |
| Example | (75 + 85 + 90 + 80) ÷ 4 = 82.5% | (3.7 × 4 + 3.3 × 3 + 4.0 × 4) ÷ 11 = 3.70 |
| Varies by school? | Grading scales vary | GPA scales and rules vary by institution |
A grade average can be a percentage or a score average, while GPA uses grade points on a specified scale. If your school reports both, the grade average answers “how did I do on these assignments?” and the GPA answers “how did I do across these courses, weighted by credits?”
Quick-Reference: Grade Averages
| Grades | Calculation | Average |
|---|---|---|
| 75, 85, 90, 80 | 330 ÷ 4 | 82.5% |
| 80%, 90%, 70% | 240 ÷ 3 | 80% |
| 70, 80, 90 | 240 ÷ 3 | 80 |
| 92, 88, 95, 85, 90 | 450 ÷ 5 | 90 |
| 65, 75, 85, 95 | 320 ÷ 4 | 80 |
Check the last row yourself: 65 + 75 = 140; 140 + 85 = 225; 225 + 95 = 320; 320 ÷ 4 = 80. Evenly spaced grades always average to their midpoint — (65 + 95) ÷ 2 = 80.
3 Common Mistakes with Grade Averages
Mistake 1: Averaging percentages from different-sized groups. 90% of 100 and 70% of 10 do not average to 80%. Combine the totals: 97 out of 110, about 88.18%.
Mistake 2: Ignoring the weights. A final exam worth 40% should not count the same as an assignment worth 5%. If the syllabus gives weights, the grade is a weighted average.
Mistake 3: Confusing a grade average with a GPA. A percentage average and a GPA use different scales and different weights. Converting between them needs your school’s grade-point table.
And when the data has outliers — one failed test among strong scores — remember that the mean can be pulled away from the typical value. Our guide to average vs median vs mode shows when the median tells the truer story.
Check Your Work with Calcrio’s Free Tool
The free tool at Calcrio calculates simple averages, weighted averages, and grade averages — enter your scores, add weights where they apply, and it returns the average with the sum, count, minimum, maximum, and range. It is free, with no sign-up, and the fastest way to check a grade average before report-card season.
Frequently Asked Questions
How do I find the average of my grades?
Add all your grades together and divide by how many there are. For 75, 85, 90, and 80: (75 + 85 + 90 + 80) ÷ 4 = 82.5%. If the grades have different weights, use a weighted average instead.
How do you calculate the average of percentages?
If the percentages are equally weighted, add them and divide by the count: the average of 80%, 90%, and 70% is 80%. If they represent different sample sizes, combine the underlying totals instead.
Can I average two percentages directly?
Yes, when they are equally weighted. 90% and 70% average to 80% — but only if both percentages describe the same-sized groups. 90% of 100 students and 70% of 10 students combine to about 88.18%, not 80%.
What is the difference between a grade average and a GPA?
A grade average is usually a percentage average of scores. A GPA uses grade points on a scale (often 0–4.0) weighted by credit hours. They measure different things and use different scales.
What if my grades have different weights?
Use a weighted average: multiply each score by its weight, add the results, and divide by the total weight. For homework 90% (20%), quizzes 80% (20%), midterm 85% (25%), final 92% (35%): the weighted average is 87.45%.
Is the average of my test scores the same as my final grade?
Not necessarily. Your final grade is usually a weighted average of categories (homework, quizzes, exams) with different weights. A plain average of test scores only matches the final grade if every category counts equally.