Unfortunately the federal student aid EFC estimator is less detailed and less accurate than other resources including collegeboard’s EFC estimator, here: Expected Family Contribution (EFC) Calculator – BigFuture | College Board
For example, the federal student aid estimator doesn’t add back to income 401k contributions,or necessarily include all child support payments, which must be added into FAFSA income. Of course, students should also complete each school’s NPC.