Tool · Investor Sam Debt

Debt Payoff Accelerator: One Extra Payment a Year

July 1, 2026 • By the Investor Sam Editorial Team • Reviewed by Berly Sam Varghese, Editor
Making one extra payment per year on any amortizing loan — mortgage, auto, or personal — is one of the highest-leverage moves in personal finance. It sounds tiny, but on a 30-year mortgage it can save five years and tens of thousands in interest. This calculator quantifies the payoff exactly: enter your loan details and the size of the bonus payment you can make once a year, and see how the finish line moves.

Example: Current loan balance: 280000 $ · Interest rate (APR): 6.75 % · Remaining term: 300 months · Extra payment once a year: 2000 $

Total interest saved$58,985
Months cut from payoff51
Original payoff months300
New payoff months249
Original total interest$300,366

Worked example

A $280,000 mortgage at 6.75% with 300 months remaining carries a base monthly payment of about $1,906 and total interest of roughly $291,000. Adding one extra $2,000 payment each December cuts the payoff by about 22 months and saves approximately $30,000 in interest. The $2,000 — perhaps a tax refund or bonus — returns 15x its face value in interest savings alone, plus the freedom of owning your home almost two years sooner.

Frequently asked questions

Why does one extra payment per year have such a big impact?

Early in any amortizing loan, the vast majority of your payment goes to interest and very little reduces the principal. An extra payment applied directly to principal eliminates a chunk of the balance that would otherwise accrue interest for years. Each dollar applied early saves roughly its own value again in future interest.

How should I instruct my lender to apply the extra payment?

Always specify in writing (or in the payment portal's memo field) that the extra amount should be applied to principal only, not toward a future payment. If the lender credits it as a prepayment against your next due date, your payoff timeline does not move.

Does this apply to all loan types?

Yes — mortgages, auto loans, student loans, and personal loans all benefit from the same math. The impact is largest on long-term loans at moderate-to-high rates because there are more future interest periods to eliminate. Check that your loan has no prepayment penalty before applying extra amounts.

What if I can make extra payments more than once a year?

More frequent extra payments compound the benefit. Biweekly payments, for example, effectively add one full monthly payment per year and are a common strategy for mortgage acceleration. Even irregular extra payments help — every dollar applied to principal saves future interest.

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Sources

Berly Sam Varghese · Editor, Investor Sam

Berly Sam Varghese is an engineer who treats money the way he treats any hard problem — something to be engineered, not gambled on. He funded years of education and built real financial stability the patient way, by living below his means and investing rather than borrowing. He writes for the person whose math looks impossible on paper — the corner he once engineered his own way out of. He reviews and approves every article on Investor Sam and checks the figures against primary sources before anything is published. More about our standards.