ReckonBoxHow the refinance calculator works
A refinance replaces your existing mortgage with a new one, so what it costs is the difference between two whole loans, not the difference between two monthly payments. Enter what you owe, the rate you pay, and how many months are left, then the new rate, the new term and the closing costs. The tool returns two break-even figures, and the gap between them is the point.
Start with the default. A $342,057 balance with 276 months left at 6.55% costs $2,401.66 a month. Refinance to 5.75% over a fresh 30 years and the payment drops to $1,996.15, a fall of $405.50. That looks decisive. Over the full term it adds $61,757 to what you pay in interest.
The break-even everyone publishes, and what it misses
The standard break-even formula is closing costs divided by the monthly payment saving, and it treats every dollar the payment falls by as money saved. Freedom Mortgage works it as $8,000 over $225 to get 35.56 months. Chase works $5,000 over $200 to get 25 months. Quicken Loans and NerdWallet publish the same division. It's the only break-even arithmetic on any refinance page we fetched.
The trouble is that a payment can fall for two completely different reasons. The rate can drop, which is a saving. Or the remaining balance can be stretched back over a longer term, which is not.
The rate doesn't have to move at all for the payment to fall:
| Current | Refinanced at the same 6.55% | |
|---|---|---|
| Monthly payment | $2,401.66 | $2,173.29 |
| Months left | 276 | 360 |
| Interest still to pay | $320,800 | $446,328 |
The payment falls $228.36. Divide $6,000 of closing costs by that and the published formula reports break-even in 2 years 3 months. In reality this refinance never breaks even and costs $125,528 more, on an identical interest rate. The formula cannot see it, because the only thing it measures is the size of the payment.
What the second figure measures
A break-even on total position compares everything you've handed over plus everything you still owe, at every month of both loans. That second term is what catches re-amortisation: a longer loan leaves a bigger balance behind at every point, so stretching the term can't flatter it.
On the default rate cut, the published formula says 1 year 3 months and the position measure says 2 years 5 months. The published figure is early because the new loan pays down more slowly at first.
Now reverse it. Take the same cut from 6.55% to 5.75%, but set the new term to 23 years so it matches what was left:
| Fresh 30 years | Held to 23 years | |
|---|---|---|
| New payment | $1,996.15 | $2,237.00 |
| Published break-even | 1 yr 3 mo | 3 yr 1 mo |
| Position break-even | 2 yr 5 mo | 2 yr 3 mo |
| Lifetime interest | $61,757 more | $39,446 less |
The published formula now reports the worse number for the option that actually saves $39,446. It's not simply optimistic. It measures payment size, so it flatters whichever choice lowers the payment most, and that's usually the one that costs you.
Where the numbers come from
Both payments use M = P times r times (1 + r) to the power n, divided by (1 + r) to the power n minus 1. The current payment is computed from your balance and the months remaining, so a loan part way through amortises on its real schedule.
The position figure walks both loans month by month. At each month it adds up payments made so far plus the balance outstanding, with closing costs counted at month zero when you pay them in cash. The first month where the refinanced position is no worse than staying put is the break-even. When that never happens, the tool says so instead of returning a number.
Closing costs are yours to supply. U.S. Bank puts the typical range at 2% to 5% of the refinance amount and MortgageCalculator.org cites the Federal Reserve at 3% to 6% of principal, but the figure that matters is on your lender's loan estimate.
What this does not decide for you
This prices two loans against each other. Whether to refinance depends on things no calculator holds: how long you'll keep the house, what else the closing cost money could do, whether a lower payment matters more to you right now than lifetime interest, and what you'd actually qualify for. A shorter term means a higher payment, which is a real constraint and not just a number. None of this is a quote, an approval, or advice. Talk to a licensed mortgage professional about your own file.
One honest alternative the tool can't quote you: if a refinance only lowers your payment by stretching the term, paying the old amount into the new loan gets you most of the way there without the fees.
Frequently asked questions
How do you calculate the break-even point on a refinance? The formula published across the field is closing costs divided by the monthly payment saving. It is easy and it measures the wrong thing, because part of a lower payment is the same debt spread over more years. This tool also computes a break-even on total position, which is everything you have paid plus everything you still owe, and that one cannot be fooled by a longer term.
Why does refinancing at the same rate lower my payment? Because the remaining balance is being re-amortised over a longer period. On a $342,057 balance with 276 months to run at 6.55%, going back to a fresh 30 years at the identical 6.55% drops the payment from $2,401.66 to $2,173.29. Nothing was saved: that refinance costs $125,528 more in interest and never breaks even.
Does a lower monthly payment mean I am saving money? Not by itself. A payment can fall because the rate fell, because the term got longer, or both, and only the first is a saving. This calculator flags the case where the payment drops while lifetime interest rises, which is the exact scenario the widely published break-even formula reports as a win.
Should I match the new term to the years left on my old loan? Comparing like with like requires it, and the tool defaults the term field so you can set it either way. On the default figures, cutting 6.55% to 5.75% over a fresh 30 years raises lifetime interest by $61,757 despite the lower payment, while the same rate cut held to the remaining 23 years saves $39,446.
What are typical refinance closing costs? U.S. Bank puts the range at 2% to 5% of the refinance loan amount, and MortgageCalculator.org cites the Federal Reserve at 3% to 6% of principal. Neither is a quote for your file. The number that matters is the one on your lender loan estimate, which is what this field is for.
Is it better to pay closing costs upfront or roll them in? Rolling them in means no cash at closing and a larger balance carrying interest for the whole term, so the same fee costs more. Paying upfront means the money leaves today. The tool prices both, and the difference shows up in the break-even and the lifetime interest rather than in the monthly payment.
What is the difference between this and paying extra on my current loan? Refinancing replaces the loan and charges fees to do it; overpaying keeps the loan and charges nothing. They answer different questions, and the mortgage payoff calculator handles the second one. A refinance that only lowers the payment can be undone by paying the old amount into the new loan, which is the closest thing to a free version of the same result.