What One Extra Mortgage Payment a Year Actually Does
A single extra payment annually can shave years off a 30-year mortgage and tens of thousands in interest — every dollar goes straight to principal at the loan's rate. The mechanics, the numbers, and when not to do it.
Published · Home & Mortgage · 2 min read
Extra mortgage payments look unremarkable — one more payment, once a year — and produce results that look like arithmetic errors: four-plus years gone from a 30-year term, interest savings in the tens of thousands. No trick is involved. Every extra dollar bypasses interest entirely and lands on principal, and principal removed early stops accruing interest for decades.
Why the effect is so large
An amortizing loan charges interest each month on the remaining balance. Prepay $2,000 in year two of a 6% loan and you do not save $120 once — you save 6% on that $2,000 for every remaining year, compounding, because the balance is permanently lower from that point on. Early extra payments are the most powerful for exactly this reason: they have the most years left to work. The same $2,000 in year 27 barely moves anything.
The standard flavors
- One extra payment a year — from a tax refund or a three-paycheck month. On a typical 30-year loan this alone cuts roughly four to five years.
- Rounding up — a $1,847 payment made as $1,900 or $2,000. Painless, and it compounds the same way.
- 1/12 extra monthly — the arithmetic behind biweekly payment plans, without the fees some servicers charge for them.
Whatever the flavor: confirm the servicer applies extras to principal, not to next month's payment — an "advance payment" earns you nothing.
When extra payments are the wrong move
Prepaying a mortgage earns exactly the mortgage rate, guaranteed. That is excellent against a 7% loan and mediocre against a 3% one — money aimed at a 3% mortgage while a 22% card balance exists, a 401(k) match goes uncaptured, or no emergency fund stands is money misallocated. Prepayments are also illiquid: the equity cannot be un-prepaid in a crisis without borrowing it back. Order of operations first; then, if the mortgage is the best remaining use, prepay with a clear conscience.
The extra payment calculator shows your exact loan's response — years removed, interest saved, the new payoff date — for any extra amount, one-time or recurring. Few financial moves show their whole future this precisely.
Run your own numbers
More on home & mortgage
- Biweekly Mortgage Payments: A Good Trick You Should Not Pay For
- Rent vs. Buy: The Honest Version of the Math
- When Refinancing Actually Makes Sense (and When It Just Resets the Clock)
This article is general education, not tax, legal, investment, or financial advice. Figures used in examples are illustrations, not quotes or predictions. For decisions that depend on your full situation, talk to a qualified professional.