The required portion of the ACT is divided into four multiple choice subject tests: English, mathematics, reading, and science reasoning. Subject test scores range from 1 to 36; all scores are integers. The English, mathematics, and reading tests also have subscores ranging from 1 to 18. (The subject score is not the sum of the subscores.) The composite score is the average of all four tests. In addition, students taking the writing test receive a writing score ranging from 2 to 12, a combined English/writing score ranging from 1 to 36 (based on the writing score and English score), and one to four comments on the essay from the essay scorers. The writing score does not affect the composite score.
On the ACT, each question correctly answered is worth one raw point. Unlike the SAT, there is no penalty for marking incorrect answers on the multiple-choice part of the test. Therefore, a student can answer all questions without suffering a decrease in their score for questions they answer incorrectly. This is parallel to several AP Tests eliminating the penalties for incorrect answers. To improve the result, students can retake the test: 55% of students who retake the ACT improve their scores, 22% score the same, and 23% see their scores decrease.
English
The first section is the 45-minute English test covering usage/mechanics and rhetorical skills. The 75-question test consists of five passages with various sections underlined on one side of the page and options to correct the underlined portions on the other side of the page. More specifically, questions focus on usage and mechanics - issues such as commas, apostrophes, (misplaced/dangling) modifiers, the colons, and fragments and run-ons - as well as on rhetorical skills - style (clarity and brevity), strategy, transitions, and organization (sentences in a paragraph and paragraphs in a passage.)
Mathematics
The second section is the 60-minute, 60-question mathematics test with 14 covering pre-algebra, 10 elementary algebra, 9 intermediate algebra, 14 plane geometry, 9 coordinate geometry, and 4 elementary trigonometry. Calculators are permitted in this section only. The calculator requirements are stricter than the SAT's in that computer algebra systems are not allowed; however, the ACT permits calculators with paper tapes, that make noise (but must be disabled), or that have power cords with certain "modifications" (i.e., disabling the mentioned features), which the SAT does not allow. Also, this is the only section that has five instead of four answer choices.
Reading
The 35-minute, 40-question reading section measures reading comprehension in four passages (taken and edited from books and magazines) one representing prose fiction (short stories and novels), another representing social science (history, economics, psychology, political science, and anthropology), a third representing humanities (art, music, architecture, dance), and the last representing natural science (biology, chemistry, physics, and the physical sciences), in that order.
Science reasoning
The science reasoning test is a 35-minute, 40-question test. There are seven passages each followed by five to seven questions. There are three Data Representation passages with 5 questions following each passage, 3 Research Summary passage with six questions each, and one Conflicting Viewpoints passage with 7 questions.
Writing
The optional writing section, which is always administered at the end of the test, is 30 minutes long. All essays must be in response to a given prompt. The prompts are about a social issue applicable to high school students. The essay can affect the score of the English section only. If a student were to score a 10 out of 12 on the writing, and the student scored an English composite score of 25 then the score would be affected, but would most likely stay the same. If a student were to score poorly on the writing section, then the score would be reduced from 25 to 23 at the most. No particular essay structure is required. Two trained readers assign each essay a score between 1 and 6, where a score of 0 is reserved for essays that are blank, off-topic, non-English, not written with no. 2 pencil, or considered illegible after several attempts at reading. The scores are summed to produce a final score from 2 to 12 (or 0). If the two readers' scores differ by more than one point, then a senior third reader decides.
Although the writing section is optional, several schools do require an essay score and will factor it in the admissions decision.
Averages
For the original standardization groups, the mean composite score on the ACT was 18, and the standard deviation 6. These statistics vary from year to year for current populations of ACT takers.
The chart below summarizes each section and the average test score based on graduating high school seniors in 2009.
| English | 75 | 45 | 20.6 | 18 | usage/mechanics and rhetorical skills |
| Mathematics | 60 | 60 | 21.0 | 22 | pre-algebra, elementary algebra, intermediate algebra, coordinate geometry, geometry, and elementary trigonometry |
| Reading | 40 | 35 | 21.4 | 21 | reading comprehension |
| Science | 40 | 35 | 20.9 | 24 | interpretation, analysis, evaluation, reasoning, and problem-solving |
| Optional Writing Test | 1 essay prompt | 30 | 7.7 | writing skills | |
| Composite | 21.1 |
Highest Score
The chart below summarizes how many students achieved a score of 36 on the ACT between the years of 1997 and 2011.
| 2011 | 705 | 1,623,112 | 0.04337 |
| 2010 | 588 | 1,568,835 | 0.03748 |
| 2009 | 638 | 1,480,469 | 0.04309 |
| 2008 | 428 | 1,421,941 | 0.03010 |
| 2007 | 314 | 1,300,599 | 0.02414 |
| 2006 | 216 | 1,206,455 | 0.01790 |
| 2005 | 193 | 1,186,251 | 0.01627 |
| 2004 | 224 | 1,171,460 | 0.01912 |
| 2003 | 195 | 1,175,059 | 0.01659 |
| 2002 | 134 | 1,116,082 | 0.01201 |
| 2001 | 89 | 1,069,772 | 0.00832 |
| 2000 | 131 | 1,065,138 | 0.01230 |
| 1999 | 85 | 1,019,053 | 0.00834 |
| 1998 | 71 | 995,039 | 0.00714 |
| 1997 | 74 | 959,301 | 0.00771 |