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Pay Off the Mortgage or Invest?

Extra money each month: to the mortgage, or invested? Every piece below can be linked to, so it opens in a window on your reader's screen, current as of the record. No form to fill in.

2026 law · Reviewed September 7, 2026 · The full page, with methodology and sources · the terms · All tools

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The balance, rate, years left, extra per month, expected return, and whether the interest is deducted in; the months and interest saved, the two paths drawn as lines, and the position each way out. In a frame it carries no cookies, no tracking, and a visible link back to the methodology. Your site has to allow frames; most do. The link that opens it in a small window is on the professionals page.

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In plain words.
Paying extra on a mortgage earns the mortgage rate, for sure, and ends the loan early. Investing the same money earns whatever the investment returns, which is not for sure. This tool runs both month by month for the years left on the loan. On the first path the extra goes to the mortgage until it is gone, and then the whole payment is invested. On the second the extra is invested from the start while the mortgage runs to its end. It shows the months and interest saved, and the position each way at the end.
Why it matters.
It is one of the most common questions a household with a little room in the budget asks, and the answer is usually argued on feeling. A number for each path lets the feeling, which is about certainty and about being debt-free, be weighed against the size of the gap.
An example.
$300,000 at 6% with 25 years left and $500 a month extra, against a 7% return: to the mortgage, the loan ends 8 years and 11 months early and about $112,299 of interest is saved, and the position at the original end date is about $363,745. Invested instead, about $405,036, so investing is ahead by about $41,291 at that return.
Where it stops.
The expected return is a guess, and it decides the answer. The tool holds the rate and the return steady, pays no tax on the investment's growth, and deducts the interest only if you say you itemize. It leaves out mortgage insurance, prepayment penalties, the emergency fund you should keep first, and the risk that the investment does something the average does not.

Everything here reads from one reviewed record, so a copied piece carries its year and its review date. When the law moves, the embed updates by itself; a copied table or chart keeps the year in its caption. Corrections are welcome through the contact page.