Refinance Calculator (3f) Refinancing an FRM With Balance Pay-down Who This Calculator is For: Borrowers trying to decide whether paying down the balance on their existing FRM in order to lower the cost of refinancing into another FRM would yield a satisfactory rate of return. What This Calculator Does:This calculator derives the rate of return on investment in a balance pay-down plus settlement costs that reduces refinance costs, relative to holding the existing mortgage, and relative to a refinance without the pay-down.