How 42 out of 100 works out to 42%
Divide the score by the total and multiply by a hundred: 42 ÷ 100 × 100 = 42%. On a hundred-point test the two numbers are the same, which is the only test length where that is true and the reason so many gradebooks are built around it.
In lowest terms 42 out of 100 is 21 out of 50 — the same fraction with 2 divided out of both halves. That is worth noticing when a score looks unfamiliar: 21 out of 50 is the shape most people can read at a glance.
58 questions were wrong out of 100, and together they cost 58%. If any of them were marked with partial credit the real figure is a little higher — the test grade calculator takes half marks.
42% as a letter grade
Schools do not all cut letters at the same percentage, so 42% has more than one correct answer. Here is where it lands on the three scales in common US use:
| Scale | Where 42% lands | Grade points |
|---|---|---|
| Plus/minus, the most common US scale | F | 0.00 |
| Straight letters, 90/80/70/60 | F | 0.00 |
| Seven-point, 93/85/77/70 | F | 0.00 |
On the plus/minus scale this site uses throughout, 42 out of 100 is an F, worth 0.00 grade points on an unweighted 4.0 scale. A school that grades in straight letters would record it as an F too. A seven-point scale reads it as an F 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.
What it takes to reach a D-
The next letter up is a D-, which starts at 60%. On a hundred-question test that is 60 out of 100 — 18 more correct answers than you have.
What 42 out of 100 needs to pass
A hundred-question test allows 40 wrong answers before a 60% pass mark is missed. This paper has 58 wrong — 18 too many — which puts the shortfall at 18% of the grade, or 18 more correct answers (60 out of 100). That is a gap of substance rather than a marking argument.
A single failing test is not usually a failing course. If this paper is worth 20% of the grade and everything else is at 85%, the course still sits at 76.4% — the table further down shows the other weightings. The number that decides the outcome is the course grade, not this one, and the final grade calculator will tell you what the remaining work has to be.
The scores either side of 42 out of 100
One more correct answer is 43 out of 100, 43% — still an F. One fewer is 41 out of 100, 41% — still an F. Nothing exists in between. A hundred-question test has exactly 100 achievable grades above zero and 42% is one of them; a percentage that is not a multiple of 1% cannot come off a test this length, whatever a rounding rule does to it afterwards.
What 42% 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 | 80.7% | B- |
| 20% of the course | 76.4% | C |
| 30% of the course | 72.1% | C- |
| 40% of the course | 67.8% | D+ |
Because 42% is below that 85% baseline, this test pulls the course average down by 8.6 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.
42% on other test lengths
42% is not unique to a hundred-question test. The same percentage comes out of 21 out of 50. The letter grade is identical on all of them, because the letter only ever looks at the percentage. What differs is the granularity: 42 out of 100 moves in steps of 1%, while 21 out of 50 moves in steps of 2%, so the longer test can express grades the shorter one simply cannot reach.
About hundred-question tests
A hundred-point test or assignment, where the score and the percentage are the same number and every letter boundary is reachable exactly. Every score on one, from 1 to 100, is charted on the out of 100 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.