I took only federal subsidized and unsubsidized loans through 5 years of college. I now have 13 separate loans, with varied interest rates, four are 3.15%, two are 4.25, and seven are 6.55% (and those 6.55%'s also have the highest balance of them all). Thing is, when consolidating loans, it averages the interest rates together. So consolidating just my highest rates together will do nothing, but consolidating my low interest rates with the high ones will also increase my interest rate effectively on those lower interest loans. Is there a general rule for pairing certain numbers of high and low interest loans together to get the biggest reduction in money paid over time? Is there a really good calculator out there where I can test which combinations of loan consolidation will net me the most savings? Thanks!