Pay Down the Mortgage or Invest the Difference? A Break-Even Comparison
October 21, 2026
Homeowners with spare cash face a classic choice: make extra mortgage payments or invest. Mathematically, paying down a loan earns a guaranteed return equal to the loan's interest rate, because every dollar of principal repaid stops interest at that rate. Investing has a higher expected return in the long run but with risk. The break-even depends on the mortgage rate, the investment return, taxes, and your preference for certainty.
Take a $320,000, 30-year mortgage at 6.5% with a payment of $2,022.62. Adding $500 a month pays it off in 18 years (216 months) and saves $185,552 in interest.
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Open the Mortgage Calculator →Two Strategies to Compare
Strategy A: pay an extra $500 a month. The loan ends after 18 years; then invest the full $2,522.62 (the old payment plus extra) for the remaining 12 years of the original 30-year period. Strategy B: pay the regular schedule and invest $500 a month for all 30 years. At the end of 30 years, both strategies own the house outright, so we compare investment balances.
At a 7% investment return, Strategy B ends with $609,985, while Strategy A ends with $566,820 from investing after payoff. B comes out about $43,000 ahead. At 5%, A wins: $496,360 versus $416,129.
| Investment return | A: prepay then invest | B: invest $500 throughout | Winner |
|---|---|---|---|
| 3% | $436,600 | $291,368 | A (prepay) |
| 5% | $496,360 | $416,129 | A (prepay) |
| 6.5% | $548,092 | $553,089 | About equal |
| 7% | $566,820 | $609,985 | B (invest) |
| 9% | $650,108 | $915,372 | B (invest) |
Break-Even Logic
The break-even return is close to the mortgage rate, here 6.5%, which is the guaranteed return from paying off the loan. If you believe your after-tax investment return will exceed that, investing wins on average. Stocks have historically returned about 7% to 10% before inflation over long periods, but with big swings, and nothing guarantees future returns. Bonds and savings accounts usually yield less than a 6.5% mortgage rate, in which case paying down the debt beats them.
When mortgage rates were 3%, investing was an easy decision for most people; at 6.5% to 7%, prepaying is more competitive, especially for risk-averse investors.
Taxes, Liquidity, and Risk
Mortgage interest may be tax deductible if you itemize, lowering the effective borrowing cost, while investment gains may be taxed. Investing in a tax-advantaged retirement account with an employer match beats both options: capture the match first. Liquidity matters: money paid into a mortgage is locked in the home and accessible only through selling or borrowing, while invested money can be sold. Also consider the psychological benefit of owning your home free and clear versus the risk of market downturns. A mix can be sensible: invest part and prepay part.
Practical Steps
Build an emergency fund and capture any retirement match first. Pay off higher-rate debts, such as credit cards and car loans. Then decide between prepaying and investing based on your mortgage rate, risk tolerance, and age. Make sure extra payments go to principal. Confirm that your mortgage has no prepayment penalty. You can also use lump-sum payments after bonuses or tax refunds.
Frequently Asked Questions
Is it better to pay off my mortgage early or invest?
It depends on your mortgage rate versus expected after-tax investment returns, as well as your risk tolerance.
What return do I earn by prepaying a mortgage?
The mortgage interest rate, guaranteed.
Should I invest in a retirement account first?
Yes, especially if your employer offers a match.
How much does an extra $500 a month save?
On a $320,000 loan at 6.5%, about $185,552 of interest and 12 years off the term.
Is mortgage interest tax deductible?
In some countries and situations, if you itemize. Check current rules.