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Prepayment Mortgage Reduction

See how extra monthly or biweekly payments shorten mortgage payoff and cut interest compared to the standard schedule.

Results

Base monthly payment
$1,799
Payoff months (standard)
360
Payoff months (with extra)
313
Payoff months (biweekly, if selected)
166.15
Total interest (standard)
$347,515
Total interest (with extra)
$294,168
Total interest (biweekly)
$347,515
Months saved (extra)
47
Months saved (biweekly)
193.85

How to use this calculator

  1. Enter your remaining loan balance (or original balance if you’re modeling from the start), interest rate, and term in years.
  2. Enter the extra monthly payment you’re considering applying toward principal.
  3. Toggle biweekly payments if you want to see how switching from monthly to biweekly payments changes payoff time and interest.
  4. We compute base monthly payment, then simulate standard, extra, and biweekly schedules.
  5. Review payoff months, total interest, and months/interest saved for each alternative compared with the standard schedule.

Inputs explained

Biweekly
If yes, we use 26 half-payments per year with half of the extra applied each period.
Loan balance
Current or initial principal balance of your mortgage or loan. Use the remaining balance if you’re modeling prepayments on an existing loan.
Interest rate (APR %)
The annual percentage rate on your loan. This calculator assumes a fixed rate and converts it to a monthly (or per‑period) rate for the simulation.
Term (years)
Total loan term in years (for example, 30, 20, 15). For an in‑progress loan, you can approximate the years remaining to project from today forward.
Extra monthly payment
The additional amount you plan to send every month beyond the required principal-and-interest payment. This is applied directly to principal in the extra‑payment scenario.

How it works

We first compute the standard fixed monthly payment based on your loan balance, interest rate, and term using a standard amortization formula.

Using that base payment, we simulate a traditional month‑by‑month amortization to find payoff time and total interest with no extra payments.

For the extra‑payment scenario, we add your extra monthly amount to the base payment and simulate again to see the new payoff time and total interest.

For the biweekly scenario, we assume 26 payments per year at half the base payment (plus half the extra, if extra is on) and apply interest per period, effectively paying the equivalent of 13 monthly payments per year.

We then compare payoff months and total interest across all scenarios and show months and interest saved versus the standard schedule.

Formula

Base payment P = r × L ÷ (1 − (1 + r)^(-N)), where L is loan balance, r is monthly rate, and N is total months.\nExtra scenario: payment = P + Extra; simulate amortization to payoff.\nBiweekly scenario: use half‑payments every 26 periods per year with period rate ≈ APR ÷ 26 and simulate to payoff.

When to use it

  • Comparing standard vs extra vs biweekly mortgage payoff timelines.
  • Showing interest savings from small extra payments.
  • Testing whether rounding up your payment or switching to biweekly payments helps you meet an earlier payoff goal.
  • Helping clients or family visualize the tradeoff between current cash flow and long‑term interest savings.

Tips & cautions

  • If your lender charges fees for biweekly processing, factor that into your decision.
  • Even small extra payments can save significant interest over 30 years.
  • Simplified simulation; does not include escrow, MI removal timing, or ARM rate changes.

Worked examples

300k, 6% APR, 30 years, $100 extra

  • Loan balance = $300,000, APR = 6%, term = 30 years, extra monthly = $100, biweekly = No.
  • The calculator shows base payment, standard payoff months and interest, and payoff with extra payments.
  • Interpretation: see how many months you shave off and how much interest you save by adding $100 each month.

Biweekly vs monthly

  • Use the same loan details but toggle biweekly to Yes.
  • Compare payoffMonthsBiweekly and interestBiweekly to the standard monthly schedule.
  • Interpretation: see how the built‑in “13th payment” effect from biweekly payments changes payoff time and interest.

Deep dive

See how extra monthly or biweekly mortgage payments cut payoff time and interest compared to the standard schedule.

Enter loan details and extra payments to compare standard, extra, and biweekly payoff timelines.

FAQs

Should I choose biweekly payments or just add an extra monthly payment?
Both approaches can accelerate payoff. Biweekly effectively adds an extra payment each year, while extra monthly payments give you flexibility. Compare scenarios here and consider lender policies and potential fees.
Does this model PMI dropping off or changing escrow?
No. It focuses on principal and interest only. Real‑world payments may change when PMI drops or taxes/insurance adjust; treat this as a principal/interest payoff and interest‑savings view.

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This prepayment and biweekly mortgage calculator uses a simplified fixed‑rate amortization model and ignores taxes, insurance, mortgage insurance, and adjustable‑rate behavior. It is intended for educational and planning purposes only and is not a lender quote or personalized financial advice. Always confirm prepayment policies and biweekly program details with your lender before changing your payment strategy.