How 87 out of 100 works out to 87%
Divide the score by the total and multiply by a hundred: 87 ÷ 100 × 100 = 87%. 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.
13 questions were wrong out of 100, and together they cost 13%. If any of them were marked with partial credit the real figure is a little higher — the test grade calculator takes half marks.
87% as a letter grade
Schools do not all cut letters at the same percentage, so 87% has more than one correct answer. Here is where it lands on the three scales in common US use:
| Scale | Where 87% lands | Grade points |
|---|---|---|
| Plus/minus, the most common US scale | B+ | 3.30 |
| Straight letters, 90/80/70/60 | B | 3.00 |
| Seven-point, 93/85/77/70 | B | 3.00 |
On the plus/minus scale this site uses throughout, 87 out of 100 is a B+, worth 3.30 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 B. A seven-point scale reads it as a B 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: 3.30 becomes 3.80 in an honors class and 4.30 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 an A-
The next letter up is an A-, which starts at 90%. On a hundred-question test that is 90 out of 100 — 3 more correct answers than you have. Going the other way, 87 out of 100 is the lowest score that still counts as a B+ — you are exactly on the boundary, and one more wrong answer would have made it a B.
The scores either side of 87 out of 100
One more correct answer is 88 out of 100, 88% — still a B+. One fewer is 86 out of 100, 86% — a B. Nothing exists in between. A hundred-question test has exactly 100 achievable grades above zero and 87% 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 87% 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 | 85.2% | B |
| 20% of the course | 85.4% | B |
| 30% of the course | 85.6% | B |
| 40% of the course | 85.8% | B |
Because 87% is above that 85% baseline, this test pulls the course average up by 0.4 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.
87% on other test lengths
87% is only reachable on a hundred-question test out of the eight test lengths charted here. On every other length the nearest achievable score rounds to something else, which is the practical reason two students with the same understanding can end up with different letters: the test length decides which grades exist before anyone answers a question. Compare the charts if you want to see where the boundaries fall.
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.