Mortgage Refinance Calculator
Compare your current mortgage against a new rate and term to see how much you would save each month, how long it takes to break even on closing costs, and how the two loans compare over their lifetimes.
Compare your loan
The amount you still owe today, up to $100,000,000.
Your existing mortgage rate, from 0% through 25%.
Whole months remaining, from 1 through 600 (e.g. 300 for 25 years).
The rate you could refinance into, from 0% through 25%.
Length of the new loan in whole months, from 1 through 600 (e.g. 360 for 30 years).
Refinancing lowers your monthly payment by $416.97, breaking even on closing costs after 15 months.
- New monthly payment
- $1,703.37
- Current monthly payment
- $2,120.34
- Break-even point
- 15 months
- Lifetime savings
- $16,889.16
| Loan | Monthly payment | Lifetime interest |
|---|---|---|
| Current loan | $2,120.34 | $336,101.28 |
| New loan | $1,703.37 | $313,212.12 |
How refinance savings are calculated
Both the current and new payments use the standard fixed-rate amortization formula on the same outstanding balance, each with its own rate and remaining term. Monthly savings is simply the current payment minus the new payment. Break-even is the number of months of savings needed to recover the closing costs. Lifetime savings compares the total interest paid on each loan and subtracts the closing costs.
Payment = B × r / (1 − (1 + r)−n)Monthly savings = Current payment − New paymentBreak-even months = Closing costs ÷ Monthly savings- B
- Current loan balance
- r
- Monthly interest rate (annual rate ÷ 12)
- n
- Number of monthly payments in the term
$300,000 at 7% with 300 months left, refinanced to 5.5% over 360 months
With a $300,000 balance at 7% and 300 months remaining, the current payment is $2,120.34 per month. Refinancing the same balance to a 5.5% rate over a fresh 360-month term drops the payment to $1,703.37, a monthly saving of $416.97. With $6,000 in closing costs, you break even after 15 months, and the refinance saves about $16,889.16 over the life of the loans.
This is an educational estimate based only on the values you enter. It does not look up live rates and is not a loan offer.
What this calculator assumes
- The new loan refinances exactly the current outstanding balance, with no cash taken out or rolled in.
- Both loans are fixed-rate; adjustable or variable rates are not modeled.
- Break-even is measured only against monthly payment savings, not tax effects or the time value of money.
- Resetting to a longer term can lower the monthly payment while still raising total interest — check lifetime savings, not just the monthly figure.
- Money values are rounded to the nearest cent for display.
Mortgage refinance FAQ
What is the break-even point?
The break-even point is how long it takes for your monthly savings to add up to the closing costs you paid to refinance. If you plan to keep the home and loan past that point, the refinance starts paying for itself; if you might move or refinance again sooner, the upfront costs may not be worth it.
Why might a lower rate still cost more over time?
Refinancing into a longer term restarts the clock on amortization. A lower monthly payment stretched over more months can mean more total interest, even at a lower rate. That is why this calculator shows lifetime interest for each loan and a lifetime savings figure, not just the monthly difference.
Sources and review notes
Methodology last checked Jul 14, 2026. Formula implementation is covered by deterministic unit tests. No financial professional review is claimed yet.