Formula
How this calculator works
This is the simplest case in grading: one score, one total, one percentage. Use it for a single test, quiz or assignment. For a whole class with several assignments and weights, use the Grade Calculator instead.
percentage = points earned ÷ total points × 100
Worked example
You scored 43 out of 50 on a quiz. 43 ÷ 50 = 0.86, and 0.86 × 100 = 86% — a B on the common US scale.
Quick reference
| Score | Out of | Percentage | Letter |
|---|---|---|---|
| 43 | 50 | 86.0% | B |
| 17 | 20 | 85.0% | B |
| 68 | 75 | 90.7% | A− |
| 112 | 150 | 74.7% | C |
| 9 | 10 | 90.0% | A− |
| 38 | 40 | 95.0% | A |
Small totals swing hard. On a 10-point quiz, one mark is ten percentage points — which is the difference between an A− and a B−. On a 150-point exam, one mark is two thirds of a point.
Things worth knowing
Percentages above 100
Extra credit can push you past 100%. The calculator shows the real figure rather than capping it, and flags that it happened.
Percentage is not your class grade
One assignment does not determine a course grade unless it is the only thing graded. Weight decides that.
Letter scales vary
The letters shown follow the most common US convention. Some schools set boundaries differently or skip plus and minus entirely.
Frequently asked questions
How do I work out a percentage grade?
Divide the points you earned by the total points available, then multiply by 100. So 43 out of 50 is 43 ÷ 50 × 100 = 86%.
What letter grade is 86%?
A B on the most common US scale, which runs 83 to 86 for a B. Scales differ between schools, so check your syllabus before relying on it.
Can the percentage go above 100?
Yes, if you earned extra credit. The calculator shows the real figure rather than capping it, and flags that it happened.
Should I use this for my whole class grade?
No. Use the Grade Calculator, which handles several assignments and their weights. This one is for a single score out of a single total.
Why does one mark matter so much on a small quiz?
Because the total is small. On a 10-point quiz one mark is ten percentage points; on a 150-point exam it is two thirds of a point. Small assessments swing hard.
Does this work for any point total?
Yes, including decimals and unusual totals like 37 or 62.5. The arithmetic is the same regardless.
What if my instructor rounds?
Rounding policy varies and this calculator does not apply one. Some instructors round 89.5 up to an A−, some do not. That is a policy question rather than a maths one.
Is anything stored?
No. The calculation runs entirely in your browser and nothing is saved or transmitted.
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