Mortgage Payoff Accelerator

Visualize how extra payments accelerate principal paydown and reduce total interest paid

📖 About this tool

What it does

Standard mortgage / auto loan amortization with extra-payment modeling. Shows how additional principal payments accelerate payoff, the interest you save, and a month-by-month schedule with editable per-row prepayments.

Who this helps

Anyone shopping a mortgage, evaluating extra-payment strategies, or planning a paydown schedule. The interest-saved number from even modest extras is usually shocking.

How to use it

  1. Pick loan type (Mortgage / Auto / Custom) for sensible defaults.
  2. Enter loan amount, rate, and term.
  3. Add Extra Monthly Payment, Extra Annual Lump Sum, and a Lump Sum month if relevant.
  4. Use the editable Your Prepayment column for one-off custom prepayments in specific months.
  5. Read the summary stats and the principal-balance-over-time chart.

What it doesn't do

Doesn't model PMI, escrow, taxes, or homeowner insurance — that's a different tool (Rent vs Buy includes them). Doesn't model variable-rate / ARM products.

Loan Details

Loan Parameters

Calculated Payment

Monthly Payment (P&I)
—

Payment is calculated automatically. You may enter a higher amount below if you want to start with a fixed overpayment.

Extra Payments

🏠

Enter your loan parameters and click Calculate Amortization to see your paydown schedule.