The SAT is more focused on problem-solving and reasoning, while the ACT includes a science section.
The ACT is faster-paced, with less time per question than the SAT.
The SAT includes a no-calculator math section, while the ACT allows calculators for all math questions.
The SAT is scored out of 1600, while the ACT is scored out of 36.
Consider taking both practice tests to determine which format suits you best.