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Home Loan Extra Payments Calculator with Extra Payments

This calculator estimates how extra mortgage payments affect payoff timing and interest costs. You can model recurring monthly extras, a single one-time payment, or annual lump sums and compare estimated interest saved and shortened term.

Values are estimates based on standard amortization formulas and assume payments are applied to principal in the same period as interest accrual. The tool does not replace statements from your loan servicer or professional financial advice.

Updated Nov 19, 2025

Assumes an additional fixed amount added to each monthly payment starting immediately.

Inputs

Advanced inputs

Recurring extra options

One-time extra options

Annual lump sum options

Results

Updates as you type

Scheduled monthly payment (no extra)

$1,432.25

Months to payoff (with recurring extra)

—

Years shaved from original term

—

Estimated interest saved

—

Total payments with extra

—

OutputValueUnit
Scheduled monthly payment (no extra)$1,432.25currency
Months to payoff (with recurring extra)——
Years shaved from original term——
Estimated interest saved—currency
Total payments with extra—currency
Primary result$1,432.25

Visualization

Methodology

Calculations use the standard fixed-rate mortgage amortization formula to compute the scheduled monthly payment and then recompute payoff duration when extra principal payments are applied.

Recurring extra payments are modeled as an additional fixed amount added to each monthly payment. One-time payments are modeled as an immediate principal reduction. Annual lumps are approximated by an equivalent monthly amount (annual amount divided by 12).

Outputs are rounded to whole months for payoff timing estimates; intermediate expressions use continuous math functions and natural logarithms to compute the exact number of payments before rounding.

Worked examples

Example: $300,000 loan at 4.00% for 30 years. Paying an extra $200/month reduces the payoff period and saves interest; the calculator shows estimated months to payoff, years shaved, and interest saved.

Example: A $1000 one-time payment applied at the next payment reduces principal and shortens the amortization schedule; the tool approximates the effect by recomputing payoff with the reduced principal.

Key takeaways

Use recurring extra payments to see ongoing reduction in interest and term. One-time payments are effective at reducing principal immediately but will usually save less interest than the same amount paid regularly over time.

Results are approximations and assume consistent application of extra payments toward principal. Check your loan agreement for prepayment rules and verify results with your loan servicer.

Further resources

Expert Q&A

Is this an exact statement from my lender?

No. This tool provides an estimate based on common amortization math. Your lender or servicer may apply payments differently, and real statements should be obtained from them.

Does this account for prepayment penalties or escrow changes?

No. The calculator does not model prepayment penalties, escrow adjustments, taxes, insurance changes, or changes to interest rate. Check your loan contract for penalty terms.

How accurate are the payoff month and interest savings numbers?

Accuracy depends on assumptions: fixed interest rate, payment timing, and that extras are applied to principal each period. Results are rounded and intended for planning only. See citations for standards on algorithmic validation and software reliability.

Is my data saved or transmitted?

This configuration does not specify storage. Implementations should follow data minimization and security best practices (see NIST and ISO guidance cited).

Can I model biweekly or irregular extra payments?

This tool models monthly-frequency scenarios and approximates annual lumps. For biweekly or irregular schedules, use a dedicated amortization schedule or consult your servicer.

Sources & citations