$445,765. That's the interest on a $340,000 mortgage at 6.65% over 30 years — more than the loan itself. The 30-year fixed averaged 6.65% the week of August 20, 2026, according to Freddie Mac's weekly survey, so this is not a worst case. It's Tuesday.
A number that size attracts advice. Some of it works. A lot of it is folklore that survives because it sounds clever. Here are five claims worth sorting out before you act on any of them.
Myth 1: Biweekly payments are a clever trick
They're not a trick. They're arithmetic wearing a costume.
Pay half your mortgage every two weeks and you make 26 half-payments a year, which is 13 full payments instead of 12. The extra payment is where the savings come from — not the timing.
On that $340,000 loan, the monthly payment is $2,182.68. Adding one extra payment per year (about $182 a month) clears the loan in roughly 289 months instead of 360 and saves about $103,800 in interest. Real money. But you get the identical result by sending $182 extra with your regular payment, without enrolling in anything.
Where it goes wrong: some servicers hold the half-payment in suspense until the second half arrives, then apply the full amount on schedule. You get the inconvenience and none of the benefit. Worse, third-party biweekly programs sometimes charge $300 to $400 in setup fees for a service you can replicate for free.
Myth 2: The advertised rate is the rate you'll pay
The interest rate covers what the lender charges for the money. The APR folds in origination fees, discount points, and mortgage insurance — everything you pay to get the loan, spread across its life.
Two lenders quoting 6.5% can carry APRs of 6.6% and 6.95%. The second one is charging you roughly $9,000 more in fees on a $340,000 loan, and nothing on the rate sheet will say so.
The fastest sanity check: take the payment a lender quotes you, the loan amount, and the term, and back out the actual rate embedded in that payment. If it lands above the advertised rate, you've found the fees.
Myth 3: Extra payments automatically reduce principal
Send $500 extra and many servicers will happily apply it to next month's payment instead of your balance. Your due date moves forward. Your principal doesn't move at all — and interest keeps accruing on the same amount.
You have to say so explicitly: "apply to principal only, do not advance the due date." Some servicers require it in writing or through a specific field in their portal. Check the next statement to confirm the balance actually dropped by what you sent. This takes two minutes and is the single most common way well-intentioned extra payments get wasted.
Myth 4: Refinancing to a lower rate always wins
Lower rate, lower payment, obviously better — except the payment falling doesn't tell you what happened to the total.
Refinance in year six into a fresh 30-year term and you've just added six years of interest back onto the tail of the loan. The monthly number improves; the lifetime number often doesn't. Closing costs of 2% to 5% of the balance go on top.
The honest test has two parts. First, the break-even: closing costs divided by monthly savings gives the number of months before the refinance pays for itself. If you might move before then, stop. Second, compare total remaining interest under both scenarios — old loan with its existing payoff date versus new loan with the new one. Run both through the financing calculator using each loan's remaining term. The comparison takes five minutes and occasionally reverses the decision entirely.
Myth 5: Paying it off early always beats the alternative
Mortgage interest is one of the cheapest forms of borrowing available to an individual, and unlike credit card debt it doesn't compound against you at 22%.
Before throwing $300 a month at a 6.65% mortgage, check what else that money is competing with. A credit card at 21% is not a close contest — kill that first. An employer 401(k) match is an instant return no mortgage prepayment can approach. An emergency fund matters more than a shorter amortization schedule, because home equity is the least liquid asset you own; you cannot eat it during a layoff.
That said, $300 extra a month on this loan cuts about 8.5 years and $146,650 in interest. The guaranteed, tax-free return of prepaying is genuinely competitive once the higher-priority money is handled. It's a ranking problem, not a yes-or-no problem.
What to actually do this week
Pull your last statement. Find your rate, your remaining balance, and your remaining term. Put those three numbers into a payment calculator and see the total interest you're currently signed up for. Then try it with $100, $200, and $300 extra per month.
The gap between those scenarios is usually larger than people expect — and it's the only version of this advice that's calibrated to your actual loan rather than someone's blog post. If you're also weighing term length, the 15-year versus 30-year comparison covers the tradeoff in more detail.
Rates and figures cited reflect market data available on August 26, 2026 and will change; this article is general information, not financial advice.