How to turn a test score into a percentage and a letter grade
Convert any score such as 61/80 into a percentage and a letter grade, see common scores out of 80, and work out what you need on the final.
Updated
Tools for this job: Grade Calculator · Percentage Calculator · GPA Calculator
You got 61 out of 80. Is that good? The raw score does not say much until it is a percentage — and the percentage does not say much until you know your grading scale.
Score to percentage: one division
Divide the marks you scored by the marks available, then multiply by 100:
61 ÷ 80 = 0.7625, × 100 = 76.25%
The same method works for any score: 42 out of 50 is 84%, 17 out of 20 is 85%. The Grade Calculator does it as you type and gives the letter grade too.
It works backwards as well. To find the marks that make a given percentage, multiply the total by the percentage and divide by 100: 70% of 80 marks is 80 × 70 ÷ 100 = 56 marks.
Common scores out of 80
- 40/80 = 50%
- 48/80 = 60%
- 56/80 = 70%
- 60/80 = 75%
- 61/80 = 76.25%
- 64/80 = 80%
- 72/80 = 90%
Each mark out of 80 is worth 1.25 percentage points.
What each mark is worth on other totals
The smaller the total, the more each mark matters. This table shows the value of one mark, and the marks needed to reach 70%, 80% and 90%:
| Out of | One mark | 70% | 80% | 90% |
|---|---|---|---|---|
| 20 | 5% | 14 | 16 | 18 |
| 25 | 4% | 17.5 | 20 | 22.5 |
| 40 | 2.5% | 28 | 32 | 36 |
| 50 | 2% | 35 | 40 | 45 |
| 60 | 1.67% | 42 | 48 | 54 |
| 80 | 1.25% | 56 | 64 | 72 |
| 120 | 0.83% | 84 | 96 | 108 |
Where the table shows a half mark, such as 17.5 out of 25, you need the next whole mark up — 18 — unless your test awards half marks.
Percentage to letter grade
On the common US scale, 90% and above is an A, 80–89 a B, 70–79 a C, 60–69 a D and below 60 an F — so 76.25% is a C. On the plus/minus scale it is also a C, since C+ starts at 77%.
Boundaries are set by each school, college and exam board, and they differ widely. Some curve grades; UK degree classes use completely different bands. Treat the percentage as the reliable figure and look up your own institution's table for the letter.
To show how far the same number can travel: 76.25% is a C on the US scale above, but at a UK university, where 70% and over is a First, 60–69 an upper second, 50–59 a lower second and 40–49 a Third, the same percentage is first-class work. Neither is wrong. The tests are marked to different standards, and the bands are set to match.
Rounding, and the grade boundary problem
Whether 89.5% counts as an A is a policy, not a piece of arithmetic. Some teachers round to the nearest whole number, some round only the final course grade, and some never round at all, so that 89.99% is a B. If you are close to a boundary, read the syllabus or ask — and do the calculation with unrounded figures, because rounding each test first and then averaging can shift the answer by a point.
More than one test? Use weights
When assessments count for different amounts, a simple average is wrong. Multiply each percentage by its weight and add them up. With coursework at 84% worth 20%, a midterm at 76.25% worth 30% and a final at 70% worth 50%:
16.8 + 22.9 + 35.0 = 74.7% overall
Enter each assessment in the Grade Calculator with its weight and it does this for you. Its final exam planner works backwards too: tell it the grade you are aiming for and it tells you the score you need on the remaining exam — or says plainly if the target is out of reach.
Weights or total points? Check which your course uses
Some courses do not use weights at all. They add up every mark you earned and divide by every mark available. The two methods give different answers from the same scores. Take 42/50, 61/80 and 70/100:
- Total points: 42 + 61 + 70 = 173 marks out of 230, which is 75.2%.
- Weighted 20/30/50: 74.7%, as worked out above.
Half a percentage point is enough to cross a boundary, so check the syllabus to see which method applies before you rely on either figure.
What do I need on the final?
Carrying on with the weighted example: before the final, coursework has banked 16.8 points and the midterm 22.875, a total of 39.675 out of the 50 available so far. The final is worth the other 50%. The score needed on it is:
(target − points banked) ÷ weight of the final
- For 70% overall: (70 − 39.675) ÷ 0.5 = 60.65% on the final.
- For 80% overall: (80 − 39.675) ÷ 0.5 = 80.65% on the final.
- For 90% overall: (90 − 39.675) ÷ 0.5 = 100.65% — more than full marks, so an A is no longer possible in this course.
That last line is the useful one. Knowing a target is out of reach tells you where not to spend your revision time.
Percentage is not percentile
A percentage is how much of the test you got right. A percentile is how you did compared with everyone else: the 90th percentile means you scored higher than 90% of the people who took it. A hard exam can leave you with 61% and the 95th percentile at the same time. Standardised tests usually report percentiles; classroom tests usually report percentages.
Related calculations
For other percentage questions — a percentage of a number, or a percentage change — use the Percentage Calculator. To turn letter grades across several courses into a grade point average, see how to calculate your GPA.