Assumptions this tool makes. The loan is fixed-rate and amortised in equal monthly payments; the payment shown is principal and interest only, so it excludes property tax, homeowners insurance and mortgage insurance. The refinance is modelled as a new 30-year loan at the rate entered, with closing costs paid in cash at closing. The recast is modelled as a re-amortisation of the reduced balance over the months already remaining, with the fee paid in cash. Every path is scored as cash in hand minus balance owed at the end of the horizon, which is the position if the balance is settled at that point. The page does not model points paid to buy the refinance rate down, nor any investment return on the cash that a lower payment frees up.