The ACT and SAT are different tests that measure similar but distinct constructs. The ACT measures achievement related to high school curricula, while the SAT measures general verbal and quantitative reasoning.
ACT and the College Board have completed a concordance study that is designed to examine the relationship between two scores on the ACT and SAT. These concordance tables do not equate scores, but rather provide a tool for finding comparable scores. (Understanding concordance)
Table 1 Concordance between ACT Composite Score and Sum of SAT Critical Reading and Mathematics Scores
Table 2 Concordance between ACT Combined English/Writing Score and SAT Writing Score