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Mortgage Extra Payment Calculator

Compare a standard amortization schedule with an accelerated payment plan.

Mortgage Extra Payment Calculator estimate

Remaining mortgage balanceMortgage APR (%)Years remainingExtra monthly principal

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Your estimate

Enter values, then calculate.

How the estimate works

Two monthly amortization simulations compare the scheduled payment with the scheduled payment plus extra principal.

Important limitation

Confirm the servicer applies extra payments to principal and check for prepayment restrictions. Results are estimates only and are not financial, lending, legal, tax, or investment advice.

Assumptions and review

Formula review: July 29, 2026. This tool uses only the editable values shown above and does not pull live rates, prices, balances, or account data.

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See this calculator in a worked example

Follow the assumptions and results, then try the example with your own numbers.

What an extra $100 a month changes on a mortgage — A transparent $300,000 mortgage example: compare payoff time and interest with an extra $100 monthly, then edit the assumptions yourself.

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Frequently asked questions

How does the mortgage extra payment calculator work?