One extra payment per year cuts roughly 4 to 5 years off a 30-year mortgage, depending on your interest rate and loan balance

The math is straightforward: when you make 13 payments instead of 12 in a year, you're paying down principal faster. That extra payment goes almost entirely toward principal in the early years of your loan, because interest is calculated on the remaining balance. The lower that balance, the less interest accrues the next month.

The actual time saved varies. On a $300,000 loan at 6.5%, one extra payment per year shortens the loan by about 4.5 years. At 4%, the same extra payment saves closer to 5 years. At 8%, it saves roughly 4 years. The higher your interest rate, the more of each payment goes to interest rather than principal, so the relative impact of that extra payment is slightly smaller—but the absolute dollar savings are larger.

This assumes you make the extra payment consistently every year for the life of the loan. If you make it once or twice and then stop, the benefit is real but modest—you'll shorten the loan by a few months, not years.

Key Takeaways

  • One extra mortgage payment per year typically reduces a 30-year loan to 24 to 26 years, saving 4 to 5 years of payments.
  • The dollar amount saved depends on your interest rate and remaining balance, but generally ranges from $40,000 to $80,000 in total interest over the life of the loan.
  • The extra payment must be applied to principal, not held as a payment toward next month's regular bill.
  • The benefit compounds over time—early extra payments save more interest than late ones, because they reduce the balance on which future interest is calculated.
  • You can make one extra payment by paying half your monthly payment every two weeks, or by adding one-twelfth of your annual payment to each regular payment.

How the interest savings actually work

Interest on a mortgage is calculated daily on the outstanding balance. When you make an extra payment, you reduce that balance when ready. The next month's interest charge is calculated on the new, lower balance. That difference compounds month after month.

In the first year of a 30-year, $300,000 loan at 6.5%, your regular monthly payment is roughly $1,896. Of that, about $1,625 goes to interest and $271 to principal. One extra payment of $1,896 in year one goes almost entirely to principal because you're not paying the interest that would have accrued on that money over the remaining 29 years. That $1,896 reduction in principal means the next month's interest charge is lower, and every month after that is lower too.

By year 10, when you've paid down the balance significantly, that same extra payment still reduces principal, but the interest savings are smaller in absolute terms because the remaining balance is lower. The cumulative effect, though, is what matters: that one extra payment in year one saves far more total interest than one extra payment in year 29.

The difference between $40,000 and $80,000 in interest saved

The total interest you avoid depends on three things: your interest rate, your loan amount, and how many years you shorten the loan. A rough estimate: one extra payment per year on a $300,000 loan saves between $45,000 and $75,000 in total interest, depending on whether your rate is 4% or 8%.

On a $500,000 loan, the savings are proportionally larger—roughly $75,000 to $125,000. On a $200,000 loan, roughly $30,000 to $50,000. The pattern holds: higher balance and higher interest rate both increase the dollar amount saved.

This is why the extra payment strategy is most powerful early in the loan. If you have the cash flow to make an extra payment, doing it in year 1 or year 5 saves far more interest than waiting until year 20. By year 20, you've already paid most of the interest; the remaining balance is smaller, and the loan is shorter.

Why the timing of the extra payment matters

If you make your extra payment in January, it reduces your balance for all 12 months that follow. If you make it in December, it reduces your balance for only the remaining days of that year, then the full next year. The difference is small—a few dollars—but the principle is real: earlier payments save more interest.

The same logic applies across years. An extra payment in year 1 saves more total interest than an extra payment in year 10, which saves more than an extra payment in year 20. This is why financial advisors often recommend making extra payments as early as possible if you have the choice.

How to structure one extra payment per year

You have two practical options. The first is to make one full extra payment once per year—usually in a month when you have a bonus, tax refund, or other lump sum. You write a check or make an online payment for your full monthly amount and specify that it goes to principal, not toward next month's payment.

The second is to divide that extra payment across the year. Instead of paying $1,896 once, you pay an extra $158 per month ($1,896 ÷ 12). Or you can pay half your monthly payment every two weeks, which naturally results in 26 half-payments per year—equivalent to 13 full payments. This method requires less discipline because it's automatic, but it produces the same result.

The critical step: when you make the extra payment, tell your lender it goes to principal. Some lenders will automatically explore extra payments to principal; others will hold them as a credit toward next month's regular payment unless you specify otherwise. Check your loan documents or call your servicer to confirm their policy.

When one extra payment per year is realistic

Making one extra payment per year requires cash flow. For someone earning $60,000 per year with a $1,900 monthly mortgage, that extra $1,900 payment is 3.8% of gross income—substantial but not impossible if you have a bonus, inheritance, or other irregular income. For someone earning $40,000 per year with the same mortgage, it's 5.7% of gross income and much harder to sustain.

The strategy works best if the extra payment comes from a predictable source: a year-end bonus, a tax refund, or a spouse's part-time income. If you're stretching your regular budget to make it happen, you may be better off building an emergency fund first or paying down higher-interest debt.

It's also worth asking whether you could achieve similar results by refinancing to a shorter loan term. A 15-year mortgage at the same rate saves roughly the same amount of interest as one extra payment per year on a 30-year loan, but it requires a higher monthly payment. The choice depends on whether you value the flexibility of a 30-year payment or the certainty of a faster payoff.

What happens if you stop making extra payments

If you make extra payments for five years and then stop, you've shortened your loan by roughly 10 months to a year, depending on your rate. The benefit is real but smaller than if you'd continued. The interest you saved during those five years is locked in—you don't lose it—but you don't gain the compounding benefit of those early payments reducing the balance for the remaining 25 years.

This is why consistency matters more than the absolute amount. Making one extra payment every year for 30 years saves far more than making five extra payments in years 1 through 5 and then stopping. But making five extra payments is still better than making none.

Frequently Asked Questions

Does making one extra payment per year save more money than paying extra principal each month?

No, the total interest saved is the same. Whether you pay an extra $158 per month or one lump sum of $1,896 per year, you're reducing the principal by the same amount over the year. The only difference is timing: if you pay monthly, you save slightly more interest because each payment reduces the balance earlier. The difference is usually under $100 per year.

What if I refinance partway through my loan—do I lose the benefit of extra payments I already made?

No. Extra payments reduce your principal balance permanently. When you refinance, you refinance the new, lower balance. If you've paid down $50,000 in principal through extra payments, your new loan is $50,000 smaller, and you save interest on that amount for the remaining term.

Is one extra payment per year better than paying off the mortgage early in other ways?

It depends on your interest rate and other financial priorities. If your mortgage rate is 3%, investing extra cash in a diversified portfolio might return more than the interest you'd save. If your rate is 7% or higher, paying down the mortgage is usually the better choice. If you have high-interest credit card debt, paying that off first is almost always smarter than extra mortgage payments.

Can I make extra payments if I have an adjustable-rate mortgage?

Yes. Extra payments reduce your principal balance regardless of whether your rate is fixed or adjustable. The benefit is the same: lower balance, lower interest charges. If your rate adjusts upward, you'll be paying interest on a smaller balance, which helps offset the higher rate.

Do I need to tell my lender I'm making extra payments?

You should confirm their policy before you start. Some lenders explore extra payments to principal automatically; others hold them as a credit toward future payments unless you specify otherwise. A quick call to your servicer clarifies this and ensures your extra payment does what you intend.