A test grade is the one piece of school arithmetic everyone does in their head and half the time gets wrong, because the total is 42 and not 100. The calculator gives the percentage, the letter on both common scales, and the complete chart for your total, so a 37 out of 42 is 88.1 percent and a B+ before the paper is handed back.
Download the test grade chart (PDF) (every score as a percentage and letter for tests out of 10, 15, 20, 25, 30, 40, 50 and 100, with both letter scales; two pages, free).
The calculator
The arithmetic
Percentage = points scored / points possible x 100
37 out of 42: 37 / 42 = 0.8810, x 100 = 88.1 percent. One point on a 42-point test is worth 100 / 42 = 2.38 percentage points, so a 38 would have been 90.5 and a 36, 85.7. For tests with equal questions, the value of one question:
| Questions | One question is worth | One wrong | Two wrong | Three wrong |
|---|---|---|---|---|
| 5 | 20.0 | 80.0 | 60.0 | 40.0 |
| 8 | 12.5 | 87.5 | 75.0 | 62.5 |
| 10 | 10.0 | 90.0 | 80.0 | 70.0 |
| 12 | 8.3 | 91.7 | 83.3 | 75.0 |
| 15 | 6.7 | 93.3 | 86.7 | 80.0 |
| 20 | 5.0 | 95.0 | 90.0 | 85.0 |
| 25 | 4.0 | 96.0 | 92.0 | 88.0 |
| 30 | 3.3 | 96.7 | 93.3 | 90.0 |
| 40 | 2.5 | 97.5 | 95.0 | 92.5 |
| 50 | 2.0 | 98.0 | 96.0 | 94.0 |
Which is why short tests are brutal and long ones forgiving: three wrong on a 10-question quiz is a 70, three wrong on a 50-question test a 94.
The two letter scales
US schools use one of two families of scale. The plus-minus scale below is Buffalo Public Schools' published uniform scale for grades 3 to 12; the 10-point scale without pluses and minuses is the North Carolina state scale, required in every North Carolina high school since 2015-16. The 4.0 points are the ones each scale carries into the GPA.
| Percentage | Plus-minus letter (Buffalo Public Schools) | 4.0 points | 10-point letter (North Carolina) | 4.0 points |
|---|---|---|---|---|
| 97-100 | A+ | 4.0 | A | 4.0 |
| 93-96 | A | 4.0 | A | 4.0 |
| 90-92 | A- | 3.7 | A | 4.0 |
| 87-89 | B+ | 3.3 | B | 3.0 |
| 83-86 | B | 3.0 | B | 3.0 |
| 80-82 | B- | 2.7 | B | 3.0 |
| 77-79 | C+ | 2.3 | C | 2.0 |
| 73-76 | C | 2.0 | C | 2.0 |
| 70-72 | C- | 1.7 | C | 2.0 |
| 67-69 | D+ | 1.3 | D | 1.0 |
| 65-66 | D | 1.0 | D | 1.0 |
| 60-64 | F | 0.0 | D | 1.0 |
| below 60 | F | 0.0 | F | 0.0 |
The differences that matter: an 80 is a B- (2.7) on one scale and a B (3.0) on the other; a 90 is an A- (3.7) or an A (4.0); a 62 is an F on the plus-minus scale and a D on the 10-point scale. Schools that use a 7-point scale (A 93-100, B 85-92, C 77-84, D 70-76) still exist in some private schools and were the North Carolina scale before 2015. The letter is the school's reading; the percentage is the fact.
Rounding
A score of 89.5 is an A on the 10-point scale in a school that rounds to the nearest whole number and a B in one that does not. Most gradebooks round the displayed grade and most teachers follow the display; some handbooks say explicitly that 89.5 and above is a 90. The calculator shows the exact percentage to one decimal so that the rule can be applied either way. When a test is curved (the teacher adds points to every paper, or rescales so that the top score is 100), the curved score is the one to enter.
The chart for the common totals
The percentage for every score on a test out of 10, 20 and 25:
| Out of 10 | % | Out of 20 | % | Out of 25 | % |
|---|---|---|---|---|---|
| 10 | 100.0 | 20 | 100.0 | 25 | 100.0 |
| 9 | 90.0 | 18 | 90.0 | 23 | 92.0 |
| 8 | 80.0 | 16 | 80.0 | 21 | 84.0 |
| 7 | 70.0 | 14 | 70.0 | 19 | 76.0 |
| 6 | 60.0 | 12 | 60.0 | 17 | 68.0 |
| 5 | 50.0 | 10 | 50.0 | 14 | 56.0 |
| 4 | 40.0 | 8 | 40.0 | 12 | 48.0 |
| 3 | 30.0 | 6 | 30.0 | 10 | 40.0 |
| 2 | 20.0 | 4 | 20.0 | 8 | 32.0 |
| 1 | 10.0 | 2 | 10.0 | 6 | 24.0 |
The calculator prints the complete chart for any total up to 200 under its result, and the printable has the charts for 10, 15, 20, 25, 30, 40, 50 and 100.
From one test to the course grade
A test is one entry in a category, and the category has a weight: a 75 on a test in a 40 percent tests category with three other tests moves the course grade by about 10 percent of the test's distance from the category average. The weighted grade calculator does that step; the final grade calculator answers what the last test must be; and for the GPA all of it becomes, the middle school GPA calculator and the high school GPA calculator.
Download the test grade chart (PDF) (every score for tests out of 10 to 50 and 100 as a percentage and letter on both scales; two pages, free).
Where to get help
A 1-on-1 online class with a tutor who holds a master's in mathematics and teaches the US curriculum, Algebra 1 to AP Calculus, chemistry and physics, at 7 am before school, after 4 pm and on weekend mornings, US time, for US$10 to $13 an hour: the grade worked out above read together in the free 30-minute first class, the category or the course where five more points cost least found, and the term spent on exactly that. How online tutoring from India to the USA works, or the 1-on-1 online tutoring page.
Questions parents ask
1How do I calculate a test grade?
2What is each question worth?
3Is 89.5 an A or a B?
4What letter is a 7 out of 10?
5What is a good test grade?
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