Loan Refinance Break-Even Calculator and Formula

A loan refinance break-even calculator estimates how many months it takes for savings from a lower payment to cover refinancing costs. Enter your current loan balance, current and new APRs, remaining and new terms, and upfront costs; the calculator returns the new payment, monthly payment difference, and estimated break-even time.

Formula

The calculator estimates a simple payment-savings break-even point. First, it calculates the monthly payment for each loan using the fixed-rate, fully amortizing payment formula:

Payment = P × r / [1 − (1 + r)⁻ⁿ]

• P is the balance being refinanced, in dollars.
• r is the monthly interest rate, calculated as annual APR ÷ 1,200.
• n is the number of monthly payments: years × 12.

It then calculates monthly payment difference = current payment − new payment, and break-even months = upfront costs ÷ monthly payment difference. A positive difference means the estimated new payment is lower. If the new payment is the same or higher, there is no positive payment-savings break-even point; the calculator displays “Cannot compute.”

This is a simplified comparison, not a complete measure of the total financial effect of refinancing. It does not compare remaining interest, changes in principal paid, or the cost of extending the repayment period. The payment estimates use unrounded formula values internally, while the payment outputs are displayed to cents.

Worked Example

Using the calculator’s default inputs: current balance $20,000; current APR 10%; 3 years remaining; new APR 8%; new term 3 years; and upfront costs $500.

1. Current monthly rate: 10 ÷ 1,200 = 0.0083333. Current term: 3 × 12 = 36 months.
2. Current payment: 20,000 × 0.0083333 ÷ [1 − (1.0083333)⁻³⁶] ≈ $645.34.
3. New monthly rate: 8 ÷ 1,200 = 0.0066667. New term: 36 months.
4. New payment: 20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻³⁶] ≈ $626.73.
5. Monthly payment difference: $645.34 − $626.73 = $18.61 when calculated from the displayed, rounded payments.
6. Break-even estimate using the formula’s unrounded payments: $500 ÷ (approximately $18.61) ≈ 26.9 months.

Small differences in the last decimal can occur because displayed payments are rounded to cents, whereas the break-even calculation uses the underlying payment formula values.

Assumptions

• The APR stays fixed for each loan throughout its stated term.
• Payments are level monthly payments, made at the end of each monthly period.
• Interest compounds monthly at APR ÷ 12.
• Upfront costs are paid once and are not added to the new loan balance.
• The calculation excludes fees not entered, taxes, insurance, PMI, escrow, prepayment charges, and any effect from changing the loan balance.

How to Use the Result

The break-even number is the approximate number of months of payment savings needed to equal the entered upfront costs. If the calculator returns 26.9 months, the simple payment comparison reaches its cost threshold after about 27 months, provided the assumed balance, rates, terms, costs, and payment difference hold.

Gather figures for the same comparison date. Use the current principal balance rather than the original amount borrowed, and enter the time left on the current loan—not its original term. For the new loan, enter the proposed term and APR supplied in a written estimate or disclosure. Include costs that you would actually pay upfront. If costs are financed, add them to the new loan balance and recalculate with that larger balance; do not also count the same costs as upfront expenses.

Payment savings are not the same as total savings. A lower payment can result from spreading repayment across more months, which may increase total interest even if the monthly bill falls. For a fuller comparison, examine total remaining payments and interest under both options over the same period, along with how much principal each schedule repays. A break-even date alone does not show those differences.

Costs and Comparison Limits

Refinancing costs can have different names and may be paid upfront, added to the new balance, or otherwise reflected in an offer. Enter the costs that apply to the specific transaction and confirm whether any quoted figure is already included in the new principal or payment. Avoid double-counting.

The calculator treats the current balance as if it were the starting principal for a newly amortizing loan at the current APR and remaining term. Actual payment schedules can differ because of payment dates, accrued interest, variable rates, irregular payments, or lender calculations. If the balance is not the amount on which the stated payment was originally based, the estimated current payment may not match the bill exactly.

Common Mistakes and Alternatives

• Entering the original loan amount: Use the current balance for a refinance comparison.
• Mixing years and months: The inputs for terms are in years; the formula converts them to monthly periods.
• Using a rate that is not APR: Enter the annual percentage rate given for the loan, not a monthly rate. Obtain actual rate and cost figures from the lender.
• Ignoring the new term: A longer term can lower the payment without lowering the overall cost.
• Treating the estimate as a guaranteed date: Changed rates, balances, fees, or payment timing change the result.

If the new payment is not lower, this particular payment-savings method cannot produce a positive break-even time. You can still compare repayment schedules using total interest, remaining balance at a chosen month, and total payments over a common time horizon. Those are separate calculations and may give a different perspective than monthly cash-flow savings.

Frequently Asked Questions

What does a refinance break-even calculator tell me?
It estimates how long monthly payment savings would take to equal the upfront costs entered. It does not determine total savings or whether refinancing is suitable for a particular borrower.

What if my new payment is higher?
There is no positive break-even point based on payment savings if the new payment is equal to or higher than the current payment. Other comparisons, such as total interest or repayment timing, are separate from this calculation.

Should I include closing costs in the calculation?
Include applicable costs paid upfront. If they are added to the new loan balance, include them in that balance instead, and do not count them a second time as upfront costs.

Does a lower payment mean I will pay less overall?
No. A longer term may reduce each payment while increasing the number of payments and potentially total interest. Compare repayment totals and balances over the same period to understand that difference.

Why does my lender’s payment differ from the estimate?
The calculator uses a simplified fixed-rate monthly formula. The lender’s figures may reflect a different balance, term, rate structure, payment date, financed costs, or other items not represented here.

This result is an estimate, and the lender’s disclosure gives the exact figures.

Related

• Loan Balance Confirmation: What It Shows
• Loan Balance Equation: Formula and Calculator
• Loan Balance Amortization Schedule Calculator

in bal | Current balance | $ | 20000 | 1 | 100000000
in old | Current APR | % | 10 | 0.01 | 100
in rem | Current remaining term | years | 3 | 0.0833 | 50
in new | New APR | % | 8 | 0.01 | 100
in term | New loan term | years | 3 | 0.0833 | 50
in cost | Upfront refinance costs | $ | 500 | 0 | 100000000
out be | Break-even time | months | cost / (bal * (old / 1200) / (1 - (1 + old / 1200) ^ -(rem * 12)) - bal * (new / 1200) / (1 - (1 + new / 1200) ^ -(term * 12))) + 0 * sqrt(bal * (old / 1200) / (1 - (1 + old / 1200) ^ -(rem * 12)) - bal * (new / 1200) / (1 - (1 + new / 1200) ^ -(term * 12))) | 1
out oldp | Current monthly payment | $ | bal * (old / 1200) / (1 - (1 + old / 1200) ^ -(rem * 12)) | 2
out newp | New monthly payment | $ | bal * (new / 1200) / (1 - (1 + new / 1200) ^ -(term * 12)) | 2
out diff | Monthly payment difference | $ | oldp - newp | 2