How to Calculate a Grade Percentage
Last updated: October 13, 2026
A grade percentage tells you what share of the available points you earned. The formula is the same for a single assignment or a whole class, so once you know it you can check any score in seconds.
The formula
Percentage = points earned ÷ points possible × 100
- 17 out of 20: 17 ÷ 20 = 0.85, so 85%
- 43 out of 55: 43 ÷ 55 = 0.782, so 78.2%
- 9 out of 12: 9 ÷ 12 = 0.75, so 75%
The order matters. Always divide the points you earned by the points possible, not the other way around.
Points needed for a target percentage
To find how many points get you a target, multiply the target by the points possible. For 90% on a 60-point assignment, 0.90 × 60 = 54 points. This table covers common targets.
| Target | On 20 points | On 25 points | On 50 points | On 100 points |
|---|---|---|---|---|
| 70% | 14 | 17.5 | 35 | 70 |
| 80% | 16 | 20 | 40 | 80 |
| 90% | 18 | 22.5 | 45 | 90 |
| 95% | 19 | 23.8 | 47.5 | 95 |
Percentage to letter grade
A common scale is 90–100% for an A, 80–89% for a B, 70–79% for a C, 60–69% for a D and below 60% for an F. Schools differ, so check yours. The letter grade scale has the full chart with plus and minus grades.
To calculate a letter grade, find your percentage first, then match it to your school’s ranges. Letters are never averaged directly. They come from the percentage.
Calculate percentage with weights
When a class uses weighted categories, you calculate a percentage for each category first and then combine them using each category’s weight. Example: you have 90% in homework (worth 30%) and 80% in exams (worth 70%). 0.30 × 90 + 0.70 × 80 = 27 + 56 = 83%. The full method is in how to calculate a weighted grade.
Score percentage and weight are different
The percentage you scored on one assignment is not how much that assignment is worth. A 100% on a small quiz moves your class grade much less than an 80% on a final exam.
Common mistakes
- Dividing the wrong way. 17 ÷ 20 is 0.85. 20 ÷ 17 is 1.18.
- Forgetting to multiply by 100. 0.85 is the decimal. 85% is the percentage.
- Rounding too early. Keep extra decimals until the final answer, because rounding each step can push a borderline grade to the wrong side.
- Using the wrong total. If a question was thrown out or a bonus was added, the points possible may have changed.
Let the table do it
Paste your gradebook into Grade Calculator and the table fills in on its own, with your class percentage and letter grade shown as you change scores.
Frequently asked questions
How do you calculate a percentage on a test?
Divide the points you earned by the points possible and multiply by 100. Earning 17 of 20 points is 17 ÷ 20 × 100 = 85%.
How do I turn a score into a percentage grade?
The score is points earned over points possible. Divide the top number by the bottom number and multiply by 100.
How do I find what percentage I need on an assignment?
Multiply the percentage you want by the points possible. For an 85% on a 40-point assignment you need 0.85 × 40 = 34 points.
How do I calculate letter grades from percentages?
Calculate the percentage first, then look it up on your school’s scale. On a common scale, 87% is a B+ and 93% is an A.
Calculate it automatically
Paste your gradebook into Grade Calculator and the table fills in on its own. Change any score, or add an upcoming assignment, to see your class grade update.