Refinance Calculator (3e) Refinancing an ARM into a FRM to Lower Risk Who This Calculator is For: Borrowers with a ARM, worried about rising interest rates, trying to decide whether they should refinance into an FRM. What This Calculator Does:This calculator compares the total cost of retaining an existing ARM with that of refinancing into a new FRM, over a specified future period. It allows the upfront refinance costs to be financed.