Mortgage Overpayment Calculator
Compare a standard repayment mortgage with a lump-sum payment, a recurring monthly overpayment, or both.
Quick answer
Use your current balance, rate, and remaining term—not the original loan values. Add a lump sum or recurring amount to estimate time and interest saved.
Formula used
The standard payment is calculated from the current balance, monthly rate, and remaining payments. A lump sum reduces the opening balance; recurring overpayments reduce principal each month.
Worked example
If a borrower keeps the normal payment after reducing principal, more of later payments can go toward principal and the mortgage may finish earlier.
How to interpret the result
Use the comparison to test scenarios, then verify important decisions against current account documents and provider rules. A calculator is most useful when the inputs match the balance, rate, payment timing, and fees that apply to you.
Limitations
Rates can change and lenders may restrict overpayments or charge early-repayment fees. This model excludes escrow, taxes, insurance, fees, and payment-date effects.
Source and methodology
Consumer Financial Protection Bureau mortgage guidance. The source supports the general concept; ToolGemini performs the calculation locally from the values you enter and the formula described above.
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Frequently asked questions
Should I check for an overpayment limit?
Yes. Mortgage contracts can limit penalty-free overpayments or treat extra funds differently. Check the agreement or contact the servicer.
Does a lump sum reduce the monthly payment?
This calculator keeps the scheduled payment unchanged to estimate an earlier payoff. A lender may instead recast the loan and change the payment.
Are future rate changes included?
No. The entered rate is held constant for the remaining term, so variable or future renewal rates are not predicted.