Should you pay off a 4% mortgage or invest?
With a 4% mortgage and a 7% expected investment return, investing the extra money ends roughly $110,451 ahead after 30 years. But that's only the math on averages — paying off a mortgage is a guaranteed return and buys real peace of mind.
Why the mortgage rate decides it
Paying off a mortgage is a guaranteed return equal to the mortgage rate. Investing is an expected return with risk. So the comparison is simply 4% guaranteed vs ~7% (risky) expected:
- When the mortgage rate is well below your expected return (like 4% vs 7%), investing usually wins on average — your money compounds faster than the loan costs.
- When the mortgage rate approaches or exceeds your expected return, paying it off wins — and it's a certain win, with no market risk.
- Guaranteed vs risky matters. A paid-off house lowers your fixed costs and sequence-of-returns risk in retirement. Many people rationally choose the guaranteed return even when investing edges it out on paper.
Before you decide
A few things this comparison assumes you've already handled: capturing your full 401(k) match (an instant ~100% return that beats both), paying off any high-interest debt (credit cards dwarf a mortgage rate), and keeping an emergency fund. Money locked in home equity is hard to access without a sale or a HELOC — so don't pay down the mortgage with money you might need.
Every mortgage rate, same $450k scenario
The verdict flips at 8% in this scenario: below it the market's 7% expected return compounds faster than the loan costs, at or above it the guaranteed return of clearing the debt wins outright. Each row is a full 30-year projection with the extra $12,000/yr going either to principal or to the market:
| Rate | Invest path | Payoff path | Mortgage clear at | Ahead by |
|---|---|---|---|---|
| 2.5% | $2,676,752 | $2,497,944 | 48 | Invest +$178,808 |
| 3% | $2,631,773 | $2,468,066 | 48 | Invest +$163,707 |
| 3.5% | $2,586,758 | $2,462,307 | 48 | Invest +$124,451 |
| 4% this page | $2,543,245 | $2,432,793 | 48 | Invest +$110,451 |
| 4.5% | $2,500,498 | $2,403,436 | 48 | Invest +$97,061 |
| 5% | $2,457,964 | $2,374,009 | 48 | Invest +$83,955 |
| 5.5% | $2,415,329 | $2,344,279 | 48 | Invest +$71,050 |
| 6% | $2,372,243 | $2,313,940 | 48 | Invest +$58,304 |
| 6.5% | $2,328,632 | $2,282,913 | 48 | Invest +$45,719 |
| 7% | $2,284,376 | $2,252,883 | 47 | Invest +$31,492 |
| 7.5% | $2,239,458 | $2,227,290 | 47 | Invest +$12,168 |
| 8% | $2,193,925 | $2,201,783 | 47 | Pay off +$7,858 |
Assumptions: $450k home, 20% down, 30-yr term, an extra $12,000/yr toward principal, 7% investment return, 3% inflation, single filer. Mortgage interest is only deductible if you itemize — most people take the standard deduction, so this treats it as non-deductible. Model your own numbers in the calculator.
Fill the tax-advantaged buckets before you touch the mortgage
Comparing a mortgage rate to expected market returns skips a step that beats both. Before extra principal or ordinary investing, there is an order of operations that reliably wins:
- An employer 401(k) match is an immediate return of roughly 100 percent — no mortgage rate comes close.
- High-interest debt, such as a credit card balance, should clear next; its rate dwarfs any mortgage.
- An emergency fund protects everything else from a forced, badly timed sale.
Then comes tax-advantaged space. A dollar inside a 401(k), IRA, or HSA compounds shielded from tax, which lifts its effective return well above the same dollar in a taxable account. That shelter, not just the raw market return, is what a moderate mortgage rate is really competing against.
Only once the match is captured, costly debt is gone, and those sheltered accounts are being funded does the prepay-versus-invest question truly begin — and at a rate in this range, tax-advantaged investing usually still edges ahead of paying down the loan.
Common questions
Should I pay off a 4% mortgage or invest?
On average, investing wins by about $110,451 over 30 years because a 7% expected return beats the 4% guaranteed by paying it off. But paying off is guaranteed and risk-free, which many people rationally prefer.
Is it worth paying off my mortgage early?
Financially it's worth it when your mortgage rate is at or above your expected after-tax investment return. Below that, investing usually builds more wealth — though a paid-off home reduces risk and fixed costs, which has real value beyond the math.
What should I do before paying extra on my mortgage?
Capture your full 401(k) match, clear high-interest debt (credit cards), and hold an emergency fund first — each of those beats extra mortgage payments. Only then does paying down a low-rate mortgage compete with investing.