A familiar situation
If you are adding a fixed extra amount to each mortgage payment, compare the new payoff timing and interest with the scheduled plan. Confirm how your lender applies extra principal payments.
How to use this calculator
- Enter amount financed, annual interest rate, repayment term and the remaining inputs.
- Select Calculate to see the answer and its breakdown.
- Keep a scenario, change an input and compare the results.
Use consistent units and check the assumptions below before applying the result.
How mortgage amortization is calculated
The schedule applies interest to the remaining balance each month before subtracting the scheduled payment and any extra principal. Extra payments are assumed to have no prepayment penalty. Formula: Balance path applies monthly interest, scheduled payment and additional principal until payoff. Use the displayed details to inspect the intermediate amounts and replace example assumptions with terms from your own quote or records.
Balance path applies monthly interest, scheduled payment and additional principal until payoff.Extra principal reduces the balance sooner, so later interest is charged on a smaller amount.
Assumptions & useful context
The final payment may be smaller; extra payments are applied directly after monthly interest.
Financial projections use your assumptions. Actual returns, lender terms, fees and tax rules can differ; these results do not guarantee a future outcome.
Frequently asked questions
Mortgage Amortization Calculator: what does the result include?
The model applies each extra amount to principal after that month’s interest. Check your loan terms for payment instructions and prepayment restrictions.
Mortgage Amortization Calculator: which assumptions matter most?
The estimate assumes monthly timing and a fixed rate. Daily interest, payment dates, rounding and fees can shift the final installment.