Calculator Tools
Mortgage Refinance Calculator
Compare your current mortgage against a refinance offer. See monthly savings, break-even months, lifetime interest difference, and an approximate new APR.
How do you know your current balance
We derive the balance today from your original loan amount, rate, term, and how many monthly payments you have already made.
Current loan
The loan you have right now. Rates and balances are typed exactly as they appear on your statement.
New loan
The refinance offer you are evaluating. Use the rate and term from the lender estimate, plus the closing costs.
Origination, appraisal, title, and lender fees in one number. Typical US closing costs run 2 to 5 percent of the new loan.
Equity you want to pull out at closing. Added to the new loan principal.
Result
Monthly savings
$250.58
New payment is $1,932.39 vs $2,182.96 today.
Break-even point
1 yr 9 mo
Monthly savings cover the $5,500 closing costs in 21.9 months.
Lifetime interest difference
$81,187
Less total interest across the life of the new loan than what is left on the current loan.
Current monthly payment (P&I)
$2,182.96
Principal and interest on the loan you have today.
New monthly payment (P&I)
$1,932.39
Principal and interest on the refinanced loan.
Monthly savings
$250.58
Lower payment each month under the new loan.
Current loan balance today
$309,994.70
Derived from your original loan and months paid.
New loan principal
$309,994.70
Equal to your current balance for a pure rate-and-term refinance.
Closing costs
$5,500
Paid out of pocket at closing.
Break-even point
1 yr 9 mo (21.9 months)
How long it takes for the monthly savings to recoup closing costs.
Current remaining term
27 yr
How long you would keep paying the current loan if you do not refinance.
New loan term
27 yr
Length of the refinanced loan.
Interest remaining (current loan)
$397,286
Sum of interest you would still pay on the current loan from today until payoff.
Total interest (new loan)
$316,099
Sum of interest across the new loan, including any rolled-in costs and cash-out.
Lifetime interest difference
$81,187
You pay less interest overall by refinancing.
Lifetime cash difference
$75,687
Total dollars saved over the life of the refinance, net of closing costs.
New loan APR (approx.)
6.170%
Approximate APR for the new loan, including out-of-pocket closing costs. Excludes lender fees not listed.
All math runs in your browser. Loan balances, rates, and closing costs never leave your device.
Worked examples
Tap any preset to load realistic numbers. Each one mirrors a common refinance scenario.
How the math works
- Monthly payment: the fixed-rate formula M = P * r * (1 + r)^n / ((1 + r)^n - 1), where P is principal, r is the monthly rate (annual rate / 12 / 100), and n is the number of monthly payments.
- Current balance: when you give us the original loan plus months paid, we use the closed-form remaining-balance formula. When you give us a current balance directly, we use it as-is.
- Break-even months: closing costs divided by monthly savings. If the new payment is not lower, there is no break-even point.
- Lifetime interest: total interest you would still pay on the current loan from today until payoff, minus total interest on the new loan. We add cash-out back so the comparison stays apples-to-apples (the cash-out is new debt by choice, not a refinance cost).
- APR (approx.): solved by bisection on the rate that turns the net principal you receive into the same monthly payment over the same term. It includes out-of-pocket closing costs.
What to watch out for
- A lower monthly payment is not the same as a cheaper loan. A 30-year refinance of a loan with 22 years left can lower the monthly bill while increasing total interest by tens of thousands.
- No-closing-cost refinances are not free; the lender either rolls the costs into principal or hides them in a higher rate. The calculator handles both cases.
- Break-even assumes you keep the loan. If you plan to sell or refinance again before the break-even date, the closing costs are not recovered.
- Cash-out refinancing converts equity into debt and resets the amortization curve. The lifetime interest figure reflects this by treating the cash-out as separate borrowing.
- Property tax, homeowners insurance, PMI, and HOA dues are not part of the P&I comparison shown here. Use the mortgage calculator for the full PITI bill.
How to use
- Pick how you know your current balance: enter the original loan plus monthly payments made, or type the current balance plus years remaining.
- Fill in the current loan: original amount, original term, months paid, and current interest rate (or current balance, current rate, and years remaining).
- Enter the refinance offer: new rate, new term in years, closing costs, and optional cash-out. Toggle Roll closing costs into the new loan if the lender absorbs the fees.
- Read the three headline cards: monthly savings, break-even point in months, and lifetime interest difference. Green means you save, rose means you lose, blue means it is close.
- Tap any preset (rate drop, shorten to 15, cash-out, no closing cost, small rate drop test) to load a realistic scenario, or Copy summary to share the result.
About this tool
Mortgage Refinance Calculator compares the loan you have today with a refinance offer and shows whether the new loan actually pays off. Enter either your original loan plus how many monthly payments you have made, or your current balance with the years remaining; we derive the current monthly principal and interest payment from there. Then enter the refinance offer: the new rate, the new term, closing costs, and an optional cash-out amount. The result panel reports the three numbers that decide most refinance questions: monthly savings (current payment minus new payment), break-even point in months (closing costs divided by monthly savings), and the lifetime interest difference between staying on the current loan and switching to the new one. A no-closing-cost option rolls closing costs into the new principal so the comparison still works when the lender absorbs the fees up front. An approximate APR is solved by bisection so the new loan can be compared to other quotes on a like-for-like basis. Worked-example presets cover the classic scenarios: a clean rate drop with the same payoff date, shortening to a 15-year loan, cash-out refinance, no-closing-cost refinance, and the half-point-drop test. Every number is computed in your browser; balances, rates, and closing costs never leave your device. Useful for deciding whether to refinance, comparing two lender estimates, choosing between rate-and-term and cash-out structures, sanity-checking the savings figure a loan officer quoted, and finding the break-even month against the date you plan to sell or refinance again. The tool covers principal and interest only; property tax, insurance, PMI, and HOA dues are handled by the standard mortgage calculator.
Free to use. Works in your browser. No signup, no login.
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