After you submit the FAFSA, you'll receive a number called the Student Aid Index, or SAI. It replaced the old Expected Family Contribution (EFC). It's easy to misread, so here's what it does and doesn't tell you.
What the SAI is
The SAI is an index number calculated from the financial information on your FAFSA. Colleges use it as one input when working out how much financial need you have. Federal eligibility for aid like the Pell Grant is also tied to it.
What the SAI is not
It is not a bill, a price tag, or the amount your family must pay. A college's own cost and its own aid policies determine what you'd actually owe. The SAI can even be a very low or negative number, which generally signals high need rather than a mistake.
How colleges use it
In general, a college subtracts the SAI from its cost of attendance to estimate your financial need, then builds an aid package from grants, scholarships, work-study, and loans. Packages differ widely between schools, so the same SAI can lead to very different offers. Schools that also require the CSS Profile may use their own formula in addition.
What to do with your number
Don't use the SAI to rule colleges out. Compare award letters, focus on what you'd pay after grants and scholarships, and ask the financial aid office if something looks wrong or your family's situation has changed.
The honest bottom line
The SAI is a starting point, not a verdict. The real answer is in each school's award letter.