Refinance Calculator
Compare your current mortgage with a refinance scenario to estimate payment savings and break-even timing with WealthCalcLab.
Updated April 10, 2026
What this calculator does
This refinance calculator helps you compare your existing mortgage with a proposed refinance so you can judge whether the lower rate actually produces a meaningful financial benefit.
A refinance can lower the payment, reduce lifetime interest, or improve monthly cash flow, but closing costs and term resets can change the picture materially.
The most useful outputs are not just the new payment, but the break-even timing and the interest difference over the full remaining life of each option.
This page is built for users who need a defensible planning answer, not just quick arithmetic. It translates "Current mortgage balance", "Current rate", and "Remaining years" into "Monthly savings", "Break-even time", and "Lifetime interest savings" so the trade-off is visible in one place instead of being hidden behind a single number.
How to use it
Enter your current balance, current rate, and the number of years remaining on the existing mortgage.
Then enter the proposed new rate, new term, and estimated closing costs.
Compare monthly savings with break-even timing before assuming the refinance is automatically beneficial.
Start with "Current mortgage balance", "Current rate", and "Remaining years", then check whether the first output cards already answer your question. After that, add advanced assumptions such as "Closing costs" only when they are real enough to change the decision.
Method
Monthly savings = current payment - new paymentBreak-even months = closing costs ÷ monthly savingsInterest savings are compared across the full modeled remaining life of the old and new loans.
Methodology
Both the current and refinance scenarios are modeled as standard amortizing loans from the same starting balance.
Monthly savings equals the current scheduled payment minus the new scheduled payment.
Break-even months equals closing costs divided by monthly savings when monthly savings are positive.
The model maps "Current mortgage balance", "Current rate", and "Remaining years" into "Monthly savings", "Break-even time", and "Lifetime interest savings" using the formulas shown on the page. Keeping those relationships visible makes it easier to separate the core economics from the optional adjustments and to understand which assumption is actually moving the answer.
Worked example
A refinance that lowers the rate can still be unattractive if closing costs are high and you expect to sell or move before break-even.
On the other hand, even a modest rate reduction can be valuable on a large balance if you plan to keep the mortgage for years.
How to interpret the results
Positive monthly savings helps current cash flow, but break-even timing shows how long you need to keep the loan for the refinance to justify its upfront cost.
If the new term is longer than the remaining term on the current mortgage, payment relief may come at the cost of paying interest for longer.
Read "Monthly savings" first, then use the other summary cards, the chart, and the detailed table to judge short-term affordability and long-term borrowing cost. In most finance decisions, the best option is the one that stays strong across the full picture, not just the one with the most attractive first number.
Common mistakes
- Looking only at the new payment and ignoring closing costs.
- Resetting into a much longer term without considering the long-run interest effect.
- Ignoring the realistic time horizon you expect to keep the loan.
Key terms
Quick definitions for the finance terms that matter on this page.
Break-even point
The number of months required for payment savings to recover refinance closing costs.
Term reset
Starting a new loan term that can lower payment but extend debt duration.
Frequently asked questions
Clear answers on assumptions, interpretation, and the limits of each estimate.
If the new payment is lower, should I refinance?
Not automatically. You should compare closing costs, break-even timing, and the full remaining interest cost as well.
Can a refinance increase total interest even with a lower rate?
Yes, especially if the new term is significantly longer than the remaining term on the current loan.
Why does break-even matter?
Because if you do not keep the loan long enough, you may never recover the upfront cost of refinancing.
Does this calculator include cash-out refinance effects?
No. It assumes the same starting balance is refinanced for comparison clarity.
Which inputs change "Monthly savings" the most?
Start with "Current mortgage balance", "Current rate", and "Remaining years". Those assumptions usually drive "Monthly savings" far more than any optional adjustment. Once the base case is right, use advanced inputs only to reflect real fees, taxes, or timing differences.
What does "Monthly savings" tell me in practical terms?
"Monthly savings" is the fastest read on the outcome, but it should not be treated as the whole decision by itself. Use it as the headline number, then read the chart, table, and other summary cards to understand what is happening underneath.
Why should I look at "Break-even time" as well as "Monthly savings"?
Because "Monthly savings", "Break-even time", and "Lifetime interest savings" answer different parts of the same decision. A scenario can look good on the first number and still be weak once timing, total cost, or long-run value is included.
When should I use "Closing costs"?
Use "Closing costs" when it materially changes the economics of the decision. If it is uncertain or optional, compare the base case with and without it rather than guessing once and trusting the result.
What happens if the advanced options stay at zero?
Then the calculator runs a simpler base case using the main inputs only. That is often the best place to start, because it makes it easier to see what changes once optional costs, fees, taxes, or adjustments are layered in.
Does the chart add anything beyond the summary cards?
Yes. The chart shows how the result develops over time, which is often the real decision point. It is especially useful when two scenarios have a similar headline result but very different timing or cost patterns.
What is the detailed table useful for?
Use the table when you need the period-by-period breakdown behind the summary. That is usually where users spot front-loaded interest, a slow payoff path, a contribution gap, or the exact point where one scenario becomes better than another.
Should I compare more than one refinance case?
Yes. A base case and one stressed case usually give a much better planning view than a single run. Change one major assumption at a time so you can see what is actually responsible for the difference.
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Important disclaimer
For Finland, confirm local treatment of lender fees, repayment timing, and any mortgage or prepayment rules before using the output for a final application, filing, or contract decision.