One Extra Mortgage Payment a Year: How Many Years It Cuts Off

One extra mortgage payment a year is the rare money move that costs a little now and pays back a lot. On a $320,000 loan at 6.5% over 30 years, adding one extra monthly payment each year pays the loan off in about 24 years 2 months instead of 30, roughly 5 years 10 months sooner, and saves about $93,073 in interest. You can run your own loan and rate in the Mortgage Extra Payment Calculator, but here is exactly why the number is that big.

Why one payment does so much

The math looks almost unfair until you see the mechanic. Your monthly payment is fixed. On this loan it is $2,023, and it never changes. Each month the lender first takes the interest owed on the current balance, and whatever is left of your payment knocks down the principal.

Here is the part that matters. Early in a 30-year loan the balance is huge, so almost all of each payment is interest and only a sliver touches principal. The Consumer Financial Protection Bureau puts it plainly: “In the beginning of your mortgage term, you owe more interest, because your loan balance is still high.” A dollar you add on top of the required payment does not get split. It goes entirely to principal. And every dollar of principal you erase early removes all the future interest that dollar would have racked up for the rest of the loan.

So one extra $2,023 payment is not just $2,023 off the balance. It cancels years of compounding on that $2,023. Do it once a year and the cancelled interest stacks up into tens of thousands of dollars.

The clean way to make “one extra payment”

You do not have to save up a whole spare payment. Split it. One extra payment a year is the same as adding one twelfth to every monthly check. On this loan that is $169 a month on top of the $2,023, so you send $2,191 instead. Tell your servicer in writing to apply the extra to principal, not to next month’s payment or to escrow, or it does nothing useful.

The “better” marks land almost entirely on the right. The only column where the standard loan wins is the monthly outlay, because doing nothing extra is always cheaper this month. Everything you actually care about over the life of the loan, the payoff date and the total interest, goes the other way.

The 6.5% here is close to today’s rate

The example uses 6.5% because it is a round number that sits right on the current market. Freddie Mac’s weekly survey put the average 30-year fixed rate at 6.49% for the week of July 9, 2026, down from 6.72% a year earlier. That closeness is deliberate, and it matters for a reason most calculators skip over.

The higher your rate, the more each early principal dollar is worth, because it erases more future interest. At 6.5% this strategy trims almost six years. On the same loan at 4% to 5%, the same one-extra-payment habit cuts closer to four to four and a half years, not six. So treat “almost six years” as the number for a mid-6% loan, not a universal promise. Your own rate drives your own answer, which is the whole point of running it in the Mortgage Extra Payment Calculator.

The earlier you start, the more it saves

Timing changes the payoff more than most people expect. The interest a principal dollar cancels is all the interest it would have earned over the years left on the loan. In year one there are 29 years of future interest to erase, so an extra dollar is worth the most. In year 20 there are only 10 years left, so the same dollar cancels far less.

That is why starting the habit in the first few years captures close to the full $93,073, and starting a decade in captures a good chunk less. If you already have a loan and never set this up, it still helps, just not by the headline number.

Do these two things first

Prepaying a 6.5% mortgage is a guaranteed 6.5% return, and that is genuinely good. But two things beat it, and skipping them to pay the house down early is a mistake.

First, capture your full employer 401(k) match. If your employer adds 50 cents per dollar up to some share of your pay, that is an instant 50% return the day you contribute. The SEC’s Investor.gov calls not grabbing the full match “passing up free money,” and no mortgage prepayment comes close to 50%. Get the whole match before a single extra dollar goes to the loan. If you are weighing the house against the retirement account, the investing and retirement guide walks through why the match wins.

Second, clear high-interest debt. A credit card at 20-plus percent costs you far more than a 6.5% mortgage saves you. Pay that off, then come back to the house.

Biweekly plans and recasts

You will see companies offer to set up “biweekly” payments for a fee. A true biweekly plan means half a payment every two weeks, which is 26 half-payments, or 13 full payments a year. That lands within a few days of the one-extra-payment result. You do not need to pay anyone a setup or transaction fee for it. Directing the extra principal yourself is free and does the same thing.

A recast is a different tool for a different goal, and it is easy to confuse the two. With a recast you hand the servicer a lump sum, and they re-amortize the loan, which lowers your required monthly payment over the same remaining term. That helps monthly cash flow. It does not shorten the loan the way extra payments do. Extra payments keep the payment fixed and pull the payoff date closer, which is what saves the interest. Recasts often carry a small fee, usually a few hundred dollars, and not every loan allows one.

The caveats

These figures assume a fixed 6.5% rate, a fixed payment, and that every extra dollar reaches principal on schedule. They exclude property tax, homeowners insurance, PMI, and HOA dues, which are real parts of your check but do not change the payoff math on the loan itself. Before you start, confirm your loan has no prepayment penalty. The CFPB notes these are limited and usually appear only in the first few years and must be disclosed up front, and many mortgages written after 2014 cannot charge one at all, but check yours rather than assume. The exact dollars here come from the standard amortization formula and may differ by a few dollars from your servicer’s schedule because of rounding and how the final partial payment is handled. Run your real balance, rate, and term in the Mortgage Extra Payment Calculator to see your own payoff date.

For the bigger picture on loan length, down payments, and total cost, start at the buying a home and mortgages hub. And if you are still working out how much house your paycheck supports, see how much of a $60,000 salary you actually keep.