How 39 out of 50 works out to 78%
Divide the score by the total and multiply by a hundred: 39 ÷ 50 × 100 = 78%. Each of the 50 questions is worth 2%, so the grade can only land on multiples of 2% — there is no way to score 79% on a fifty-question test.
11 questions were wrong out of 50, and together they cost 22%. If any of them were marked with partial credit the real figure is a little higher — the test grade calculator takes half marks.
78% as a letter grade
Schools do not all cut letters at the same percentage, so 78% has more than one correct answer. Here is where it lands on the three scales in common US use:
| Scale | Where 78% lands | Grade points |
|---|---|---|
| Plus/minus, the most common US scale | C+ | 2.30 |
| Straight letters, 90/80/70/60 | C | 2.00 |
| Seven-point, 93/85/77/70 | C | 2.00 |
On the plus/minus scale this site uses throughout, 39 out of 50 is a C+, worth 2.30 grade points on an unweighted 4.0 scale. A school that grades in straight letters, with no pluses or minuses, would record the same score as a C. A seven-point scale reads it as a C as well. The full band table for all three, and what each letter is worth on the 4.0, 4.3 and 5.0 scales, is on letter grade to GPA.
If this grade came from a weighted class the grade points move rather than the letter: 2.30 becomes 2.80 in an honors class and 3.30 in an AP or IB class, on the usual +0.5 and +1.0 bumps. The high school GPA calculator applies those automatically.
What it takes to reach a B-
The next letter up is a B-, which starts at 80%. On a fifty-question test that is 40 out of 50 — one more correct answer than you have. Going the other way, 39 out of 50 is the lowest score that still counts as a C+ — you are exactly on the boundary, and one more wrong answer would have made it a C.
The scores either side of 39 out of 50
One more correct answer is 40 out of 50, 80% — a B-. One fewer is 38 out of 50, 76% — a C. Nothing exists in between. A fifty-question test has exactly 50 achievable grades above zero and 78% is one of them; a percentage that is not a multiple of 2% cannot come off a test this length, whatever a rounding rule does to it afterwards.
What 78% does to a course average
One test is rarely the whole grade. If everything else in the course is averaging 85% and this test is worth the share in the left-hand column, the course grade lands here:
| Test is worth | Course grade | Letter |
|---|---|---|
| 10% of the course | 84.3% | B |
| 20% of the course | 83.6% | B |
| 30% of the course | 82.9% | B- |
| 40% of the course | 82.2% | B- |
Because 78% is below that 85% baseline, this test pulls the course average down by 1.4 points at a 20% weighting. Weightings vary, and a syllabus that puts the final at 30% is a different problem from one that puts it at 10% — put your own categories into the grade calculator, or work backwards from the grade you need with the final grade calculator.
78% on other test lengths
78% is not unique to a fifty-question test. The same percentage comes out of 78 out of 100. The letter grade is identical on all of them, because the letter only ever looks at the percentage. What differs is the granularity: 39 out of 50 moves in steps of 2%, while 78 out of 100 moves in steps of 1%, so the longer test can express grades the shorter one simply cannot reach.
About fifty-question tests
A fifty-question test or a fifty-point assignment. Two points per question makes the mental arithmetic easy: double the score to get the percentage. Every score on one, from 1 to 50, is charted on the out of 50 page, and the easy grader turns the same table around for marking a stack of papers: count what is wrong rather than what is right.