8 out of 21 as a percentage is 38.1% (F)

An 8/21 is 38.1%, which is an F on the standard grading scale. That is a 0.0 GPA, and you got 13 wrong.

Next grade5 more → D13 out of 21 is 61.9%

With a 5-point curve43.1% → Fif your teacher adds 5 points

To pass (60%)5 more needed13 out of 21 is the passing line

What an 8/21 grade means

8 correct and 13 wrong on a 21-question test.
Each question is worth 4.76%, so every wrong answer costs 4.76 percentage points.
Any score from 0 to 12 out of 21 is an F.
5 more correct (13 out of 21, 61.9%) would make it a D.
It is below a 60% passing score, which needs 13 out of 21: 5 more correct.

Divide the score by the total: 8 ÷ 21 = 0.381.
Multiply by 100: 0.381 × 100 = 38.1%.
Find 38.1% on the grading scale: A is 90% and up, B 80%, C 70% and D 60%, so it is an F.

Rounded to a whole number this is 38%, and the letter grade stays the same.

Scale	Cutoffs	Letter
Standard A–F	A 90, B 80, C 70, D 60	F
Plus and minus	A 93, A− 90, B+ 87, B 83, B− 80 …	F
7-point	A 93, B 85, C 77, D 70	F

Which scale applies depends on your school or teacher; the syllabus usually says. The grading scales guide compares them.

Every possible score out of 21, with 8 highlighted. Pick any score to see its page.

Correct	Wrong	Percentage	Grade
21	0	100%	A
20	1	95.2%	A
19	2	90.5%	A
18	3	85.7%	B
17	4	81%	B
16	5	76.2%	C
15	6	71.4%	C
14	7	66.7%	D
13	8	61.9%	D
12	9	57.1%	F
11	10	52.4%	F
10	11	47.6%	F
9	12	42.9%	F
8	13	38.1%	F
7	14	33.3%	F
6	15	28.6%	F
5	16	23.8%	F
4	17	19%	F
3	18	14.3%	F
2	19	9.5%	F
1	20	4.8%	F
0	21	0%	F

No. Below 60% is an F, a failing grade on the standard US scale.

0.0 on a 4.0 scale, as an F.

With a half point, 8.5 out of 21 is 40.48%: an F on the standard scale and an F with plus and minus grades.

8 at most with a 60% passing score: you need 13 out of 21. With a 70% passing score you need 15 out of 21.