How to use
- Replace the example inputs with your loan and property figures.
- Select Calculate to update the estimate and any schedule.
- Change one assumption at a time, then compare the result with the earlier scenario.
How this calculation works
The engine constructs two schedules with identical principal and months. Only the note rate changes. It reports the monthly payment difference and lifetime interest difference, with both balance paths on one chart.
Rate effect = payment at original rate − payment at alternative rate
Worked example
Illustrative inputs — not a quote or a local average.
- Loan amount
- $320,000.00
- Interest rate
- 6.5 %
- New interest rate
- 5.75 %
- Loan term
- 30 years
Comparison monthly P&I: $2,022.62. New monthly P&I: $1,867.43. Monthly payment reduction: $155.18.
Reading the result
This is useful for understanding a quote difference before considering fees. Read a negative reduction as an increase: the alternative rate can be higher than the first. For a clean comparison, use offers obtained for the same loan type and similar timing.
Before acting on the estimate
Actual offers can include different points, lender credits and closing charges. This calculator intentionally excludes those differences. Use the points calculator when paying for a rate reduction and the refinance calculator when replacing an existing loan.

Questions, answered
Should I use APR here?
No. Use note rates for payment arithmetic; APR measures a broader borrowing cost.
Does the lower rate always win?
Not necessarily once different upfront costs and holding periods are considered.