Should I Pay Off My Mortgage Early or Invest the Money?
Recommendation
If your mortgage rate is below 5% and you have at least 15 years left on the loan, investing the extra money in a diversified stock index fund has historically beaten the guaranteed return of prepayment. Flip the answer if your rate is above 6%, you're within 10 years of retirement, or carrying the mortgage stresses you out, peace of mind has a real return.
What would flip the answer
| If this is true… | …lean toward | Why |
|---|---|---|
| Mortgage rate below 5% | Invest the extra money | Long-run stock returns (≈7% real) clear this hurdle with room to spare. |
| Mortgage rate above 6% | Pay off the mortgage early | The guaranteed after-tax return from prepayment competes hard with equity returns. |
| Within 10 years of retirement | Pay off the mortgage early | Entering retirement debt-free shrinks the income you need to generate. |
| 401(k) match not yet maxed | Invest the extra money | An employer match is an instant 50–100% return, beats any mortgage rate. |
| No emergency fund | Either | Build 3–6 months of expenses first; only then choose between A and B. |
| Loan was originated at 7%+ with PMI | Pay off the mortgage early | Prepayment that eliminates PMI is a hidden double-digit return. |
Worked example: $250k mortgage at 3.5%, 25 years left, $500/mo extra
Option A, apply the $500/month to the mortgage: you finish the loan 8.5 years early and save about $52,000 in interest. Effective return: 3.5% guaranteed.
Option B, invest the $500/month in an S&P 500 index fund at a 7% real return for the same 25 years: you end up with roughly $381,000 in today's dollars while still owing $0 on the mortgage at the original payoff date.
Pure math favors B by about $329,000. The case for A is psychological, and that case is legitimate, just not financial.
Why the math usually favors investing
A 30-year mortgage at 3.5% is one of the cheapest sources of money any private citizen can access. Compared to the long-run real return of the S&P 500 (≈7%), the spread is roughly 3.5 percentage points per year, compounded over decades, that's a six-figure swing on a typical loan.
The math gets weaker as the mortgage rate climbs. At 6%, the spread is closer to 1 point and the volatility of the market starts to outweigh the slim advantage.
Why the math isn't everything
Behavioral finance research (Shefrin, Statman, Kahneman) shows that the certainty of a paid-off house produces measurably lower financial anxiety than a portfolio of equal size. If holding the mortgage will push you to sell stocks in a downturn, the math advantage disappears.
Frequently Asked Questions
- Does the mortgage interest deduction change the answer?
- For most homeowners after the 2017 tax law it doesn't, about 90% of filers take the standard deduction and never benefit from mortgage interest. If you do itemize, knock 20–30% off the effective mortgage rate when you compare.
- What if I split the difference?
- Many people do half-and-half, extra to the mortgage and extra to investments. It rarely optimizes the math but it captures most of the psychological benefit of A and most of the return of B.
- Does this apply to a HELOC or second mortgage?
- No, HELOCs are usually variable-rate and currently sit well above 7%. Pay those down before considering either A or B above.
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