Written by Zufishan · MS Environmental Science · Updated June 2026
The formula
Almost every gradebook reduces to one formula:
Percentage = (Points earned ÷ Total points) × 100
When you add a course weight, the contribution to your overall grade is:
Contribution = (Points earned ÷ Total points) × Weight
An 85% on a homework set worth 20% of the course contributes 0.85 × 20 = 17 percentage points toward your final grade.
Quick reference examples
| Score | Percentage | Letter grade |
|---|---|---|
| 17 out of 20 | 85% | B |
| 92 out of 100 | 92% | A− |
| 34 out of 50 | 68% | D+ |
| 45 out of 50 | 90% | A− |
| 28 out of 40 | 70% | C− |
| 105 out of 100 | 105% | A+ (extra credit) |
Letter grade scale
| Percentage | Letter grade | GPA points |
|---|---|---|
| 97 to 100 | A+ | 4.0 |
| 93 to 96 | A | 4.0 |
| 90 to 92 | A− | 3.7 |
| 87 to 89 | B+ | 3.3 |
| 83 to 86 | B | 3.0 |
| 80 to 82 | B− | 2.7 |
| 77 to 79 | C+ | 2.3 |
| 73 to 76 | C | 2.0 |
| 70 to 72 | C− | 1.7 |
| 60 to 69 | D | 1.0 |
| Below 60 | F | 0.0 |
How to use this calculator
- Enter the points you earned in the first field.
- Enter the total points possible in the second field.
- Read your percentage and letter grade instantly.
- Optionally, enter the assignment weight from your syllabus to see how many points it adds to your overall course grade.
When to use this calculator
Use it when a returned assignment shows a raw score and you want the percentage and letter grade before the official gradebook updates. Use the optional weight field when you want to know whether a low score on a small assignment is worth stressing about. A 60% on a homework set worth 5% of the course only costs 2 percentage points overall. Use the Course Grade Calculator to combine all your assignments into the full course picture.
Understanding the weight field
The weight field is the percentage of your overall course grade this assignment category represents, not the number of points on the assignment. If homework is worth 20% of the course and this is one homework assignment, the weight is 20 only if this single assignment covers the entire homework category. If there are five equal homework assignments and this is one of them, the weight is 4 (one fifth of 20%).
When in doubt, leave the weight field blank and use the Course Grade Calculator to set up the full course with all assignments in their proper categories.
Common mistakes
Confusing the assignment maximum with the course weight. A 50-point assignment that counts for 10% of the course has a maximum of 50 in the Points field and 10 in the Weight field. Entering 50 in the Weight field would suggest the assignment is worth half the course grade.
Using the category weight for one assignment in a group. If quizzes are worth 15% of the course and you have six quizzes, each quiz is worth 2.5%, not 15%. Use the per-assignment weight, or leave the weight blank and calculate the full quiz category in the Course Grade Calculator.
Expecting a score above 100% to break the calculator. Extra credit can push a score above 100%. The calculator handles this correctly and assigns A+ for anything 97% and above.
Related calculators
- Course Grade Calculator for combining all assignments into an overall course grade
- Grade Curve Calculator for applying a curve to a low score
- Extra Credit Calculator to find how much extra credit is needed to lift a grade
- Weighted Grade Calculator for a weighted average across multiple items
- GPA Calculator for converting course grades to a 4.0 GPA
Disclaimer: Letter grades are assigned using the standard US plus-minus scale. Your institution may use different percentage boundaries. Always confirm your official grade with your instructor or institutional gradebook.