Mortgage Refinance Break-Even Calculator

Disclaimer: This calculator is provided for educational and estimation purposes only and does not constitute formal financial advice.

What this calculator actually answers

A refinance looks simple on the surface — lower rate, lower payment — but the honest question is when the savings pay back what the new loan cost to create. The calculator above compares the current mortgage, amortized over its remaining term at the current rate, against the refinance offer, and reports two break-even figures: the payment break-even, which divides closing costs by the monthly payment reduction, and the interest break-even, which walks both amortization schedules month by month and finds when cumulative interest saved first covers the closing costs. The chart plots that cumulative-saving line against the flat closing-costs baseline, so the crossing you see is the number you get.

The two break-even formulas

The payment break-even is the figure most refinance calculators quote, and the math is a straight division:

On the default example — $320,000 at 6.8% with 22 years left, refinanced to 5.9% over a new 30-year term — the payment falls from $2,339.70 to $1,898.04, a $441.66 saving, so the $7,000 of closing costs are “recovered” in 16 months. The interest break-even asks a stricter question: cumulative interest paid under the old schedule minus cumulative interest under the new one, month by month, until the difference covers the closing costs. Because the new loan amortizes slower, most of the early “saving” is principal deferred, not interest avoided, so the honest figure lands at month 33 instead of month 16. Both numbers are on the results row because they answer different questions — cash flow versus total cost.

The new term decides whether the rate cut is real

All rows compare the same current loan — $320,000 at 6.8% with 22 years left, $297,681 of interest remaining — refinanced at 5.9% with $7,000 of closing costs. The three rows are three different products. The 30-year minimizes the payment and maximizes the interest bill. The 20-year keeps a small monthly saving and cuts total interest by $71,884, recovering the closing costs on interest by month 29 — sooner than the 30-year term does, because the shorter term gives the rate cut less time to be diluted. The 15-year raises the payment $343.38 a month but cuts remaining interest by $134,726, and the calculator correctly reports no payment break-even at all, since there is no payment saving to recover costs against.

Closing costs decide how long “ahead” takes

All rows hold the default loan, rate cut, and 30-year new term. Closing costs scale almost linearly through the payment formula, but the interest break-even grows faster than linearly — the $3,000 case is repaid by month 13, while the $10,000 case takes until month 50. This is the argument for shopping the fee side of a refinance as hard as the rate side: shaving $3,000 off closing costs shortens the honest recovery time by 17 months.

The rate table shows when a refinance never pays

All rows refinance the default loan to a new 30-year term with $7,000 of closing costs. Below about 6%, the rate cut is deep enough that cumulative interest saved eventually covers the closing costs. At 6.3% and above, the payment still falls — the longer term does that even at a higher rate — but cumulative interest never catches up within the new loan’s life, and the interest break-even is reported as never. The negative last column is the resetting-clock penalty: over its full 30 years, even the 5.5% refinance costs $36,412 more interest than simply finishing the current loan.

What the chart shows that the table cannot

The chart draws cumulative interest saved as a line against the flat closing costs. On the default it climbs to about $2,786 after one year, crosses the $7,000 line at month 33, peaks near $15,800 around year 10, and then turns down — because the current loan ends at month 264 while the new 30-year loan keeps accruing interest for eight more years, eroding the saving to -$28,369 by the old loan’s end and -$65,612 by the new loan’s end. That peak-then-decline shape is the entire argument against a “lower rate, longer term” refinance rendered as a picture: the rate cut is real, and so is the clock it resets.

What this model does not capture

Closing costs are entered as one total rather than itemized, so discount points — which trade cash up front for a lower rate — are treated as a lump cost, which is exactly how they should be compared. The model holds the balance constant, ignoring that a refinance often rolls costs into the new loan, which changes the math only if the borrower keeps the loan to term. It does not model the mortgage-interest deduction change, escrow prepayments and refunds, or the value of the money’s time after the break-even — all secondary to the core question, but worth knowing before a lender’s “break-even in 16 months” email is taken at face value.

Using the numbers well

Enter the balance and rate from a current statement and the remaining years, not the original term — the current loan’s payment is amortized over what is left, which is the honest baseline. The mortgage payoff calculator uses that same starting point to size extra principal instead of a rate cut. Then read all three outputs together: the payment savings (is cash flow better?), the two break-even months (when does it pay back?), and the total-interest comparison (does the new term cost more over its full life?). A refinance that clears all three is rare and excellent; one that clears only the first two is a cash-flow trade being made with eyes open; one that clears only the first is a payment reduction bought with more interest, and the calculator will say so.