The payment you never see on the statement

Published 2026-09-16 · Last reviewed 2026-09-23

Extra principal is the cheapest guaranteed nominal return most homeowners can find: paying down a 6.5 percent mortgage saves interest at 6.5 percent, tax-free, with no market risk. Yet it feels like nothing, because the reward does not appear on any monthly bill - it arrives years later, as a mortgage that ends early. This page prices that invisible reward with the amortization engine the payoff calculator runs, so the time and interest saved are concrete numbers rather than a platitude.

$200 a month on a $300,000 balance

Take a $300,000 mortgage at 6.5 percent with 28 years remaining. Without extras it is scheduled to pay off in 28 years and cost $352,192 in interest. Add $200 a month to principal and the same loan pays off about 6 years early and saves $88,258 in interest - for a total of $52,800 in extra payments. That is the whole case for doing it: $52,800 paid in, $88,258 saved out, plus a mortgage that ends years sooner.

The reason the saving beats the amount paid is timing. Every month, interest is charged on the outstanding balance, and paying extra reduces that balance immediately, so every future month charges interest on a smaller number. That is why an extra payment in year two is worth far more than the same payment in year twenty: the earlier payment removes interest for more months. The same logic says a recurring $200 monthly beats an occasional larger lump, because the money does not sit idle between payments.

Before sending the money, three checks close the argument. One: confirm there is no prepayment penalty on the loan. Two: confirm the extra is applied to principal rather than treated as next month's payment - some servicers do the latter unless you write "principal only". Three: make sure you are not funding the extra by skipping an employer retirement match or a higher-yield savings account, because either of those beats a mortgage-rate return.

Where these numbers come from

• The schedule uses the same amortization steps the payoff calculator runs. Both the baseline loan and the extra-payment variant are worked out that way, so the new payoff date, the interest saved and the amount of the extras are exactly what the tool would print.
• Interest accrues monthly on the balance. One twelfth of the annual rate on the outstanding amount each month - the standard US mortgage convention, and the reason an earlier payment is worth more than a later one.
• What was deliberately left out. No property tax or insurance escrow changes, because those are unaffected by the loan balance; and no PMI, which is a separate decision that ends when the balance reaches 80 percent of the home value.

What this guide does not cover

It is not a recommendation to pay off debt before investing. When a mortgage rate is low, a diversified portfolio can plausibly beat it, and liquidity has real value in an emergency - so the honest version of this advice is to capture any employer match and hold an emergency fund first, then send the remainder to whichever gives the better guaranteed return. It also does not model a lump-sum strategy, recasting the loan, or the tax angle of a mortgage-interest deduction, all of which move the comparison in specific situations. Extra principal is a strong default, not an absolute.

Price your own extra payments in the Mortgage Payoff Calculator, see the month-by-month effect in the Amortization Schedule, weigh the whole loan against alternatives in the Mortgage Calculator, or check whether refinancing changes the plan in the Refinance Calculator.

Estimates only - not financial, tax or legal advice. Read the full disclaimer.