Extra Payment Calculator

How Extra Payments Affect Your Loan Amortization Schedule

This tool compares two modeled paths for the same starting balance: scheduled payments only, and scheduled payments plus a recurring extra amount applied to principal. The difference in interest and payoff time is conditional on the rate, dates, and payment allocation you enter. Use your loan statement for the current balance and confirm your servicer's extra-payment rules before relying on the estimate.

The Math Behind Extra Payments

In each modeled period, the schedule calculates interest on the outstanding balance, applies the regular payment, then applies the extra amount to remaining principal. The next period starts with a smaller balance. This page assumes the lender accepts the extra amount as principal reduction and does not charge a prepayment fee.

Illustration: a $300,000 balance at 6.5% APR for 30 years, with monthly payments and periodic APR ÷ 12 interest. The standard payment is about $1,896.20. Results below are rounded to the nearest month and dollar; the final payment is smaller than a regular payment.

• No extra: 360 payments; total interest about $382,633.
• +$200 per month: payoff in about 277 payments; interest about $279,185, roughly $103,449 less.
• +$500 per month: payoff in about 210 payments; interest about $202,874, roughly $179,759 less.
• +$1,000 per month: payoff in about 153 payments; interest about $141,471, roughly $241,162 less.

These figures are mathematical examples only. They exclude taxes, fees, escrow, changes in rate, skipped or late payments, and lender-specific allocation rules. Use the calculator above for different inputs and compare the assumptions with your contract.

Why Early Extra Payments Save the Most

For a fixed-rate, fully amortizing loan, principal paid earlier usually prevents interest from accruing on that amount in later periods. The savings depend on the contract's rate and day-count method, payment dates, fees, and whether the lender applies the money to principal immediately.

Extra Payments vs. Other Financial Priorities

Choosing between extra loan payments and investing depends on factors this calculator does not model, including your cash reserves, loan terms, taxes, employer benefits, forgiveness eligibility, time horizon, and tolerance for investment risk. Extra principal can reduce interest under the modeled schedule; investment returns are uncertain. This page does not recommend one choice over the other.

When you have balances with different rates, use the debt payoff planner to compare avalanche and snowball payoff orders.

Tips for Making Extra Payments Effectively

• Confirm payment allocation. Ask the servicer how to direct funds to principal and whether a separate instruction is needed. Rules vary by lender and contract.
• Consider automation if it fits your cash flow. Confirm that you can change or stop the amount and that the servicer will apply it to principal as intended.
• Model a possible lump sum. A one-time principal reduction may lower modeled interest; consider it alongside reserves, upcoming expenses, and any contract rules.
• Check fees and restrictions. Review your contract or ask the lender whether prepayment charges or other limits apply before sending a lump sum.
• Compare sustainable amounts. Model several extra-payment levels, then check the assumptions and confirm how your lender will post each amount.