THE NUMORIX GUIDE
How to use the Refinance Calculator
Last reviewed September 14, 2026
What this calculator does
The route either accepts a known remaining balance and current payment or reconstructs the current balance from original loan, original term, rate, and remaining time.
Formula and method
The route either accepts a known remaining balance and current payment or reconstructs the current balance from original loan, original term, rate, and remaining time. It adds cash-out, points, and fixed fees to form the new loan amount and financed principal, solves the new payment, and calculates monthly savings, total savings, and break-even months as total fees divided by positive monthly savings.
Variables and inputs
Choose whether the remaining balance is known. Known-balance mode uses remaining balance and current monthly payment; the other mode uses original amount, original term, and time remaining. Both use current rate, new term, new rate, new points, new costs and fees, and cash-out amount. Rates and points are percentages; amounts are dollars.
Worked example
With $250,000 remaining, a 1% point charge is $250,000 x 0.01 = $2,500. Adding $3,000 other costs gives $5,500 total fees and a financed principal of $255,500 before the new payment is solved. If monthly savings are $150, the fee break-even estimate is ceil(5,500 / 150) = 37 months.
How to interpret the result
Break-even answers how long monthly payment savings take to recover upfront fees under the entered model. Total savings also reflects the difference between current and new modeled interest and subtracts new fees. A lower payment can still cost more if the new term is longer or cash-out increases principal.
Common mistakes to avoid
Enter the current payment and current balance from the statement when known. Do not compare a new 30-year payment with only the first few years of an old loan without considering the remaining term. Include points and fixed costs in the cost comparison.
Assumptions and limitations
The engine assumes fixed-rate monthly amortization and uses a simplified current-loan reconstruction. It does not include taxes, insurance, prepayment penalties, appraisal, credit pricing, lender APR disclosures, or opportunity cost. A nonpositive monthly saving is reported with a zero break-even display.