ACT

SAT

Test duration is 3 hours and 25 minutes
(including optional Writing test-student may choose either way)Yes, there are breaks!
3 hours, 45 minutes(no option, essay is included)Yes, there are breaks!
This is an Achievement Test, and as such tests mastery of WHAT a Junior/Senior knows regarding general education progress.(The subjects are what they should have been exposed too) Assessment or Reasoning Test. This test focuses on Critical thinking and Problem Solving skills.  
Made up of five tests: English, Math, Reading, Science, and Writing. Trigonometry is included in the math! Made up of three tests: Critical Reading (3 sections); Math (3 sections); Writing, including essay (3 sections).No Trig!
The order of the tests is always the same: English, Math, Reading, Science, Essay, which is optional. The essay is always first, followed by the six, 25-minute sections (in random order) and then the two, 20-minute sections (in random order); the 10-minute Writing section is always last.
All questions are multiple-choice. With the exception of the 10 grid-in Math questions, all questions are multiple-choice.
No penalty for an incorrect response. One-quarter-point penalty for an incorrect response.
The English, Math, Reading, and Science tests are each scored 1-36.The optional Writing test is scored 1-12.

The Composite Score (1-36) is the average of the English, Math, Reading, and Science scores.

The Critical Reading, Math, and Writing tests are each scored 200-800.The essay section is scored 2-12 and makes up approximately 30% of the Writing score.
The ACT tests more advanced math concepts.The ACT has a Science section, while the SAT does not. The SAT has a stronger emphasis on vocabulary – it favors the writer.It is also more predictable and thus prepping=success!