The Core Math: Rate vs. Return
Extra mortgage payments provide a guaranteed, risk-free return equal to your mortgage rate. Investing provides an expected but uncertain return. The decision: is the expected investment return high enough to justify the additional risk relative to the guaranteed mortgage payoff return?
Extra mortgage payment vs. investment decision by mortgage rate
| Mortgage Rate | Guaranteed Return (extra payment) | Required Investment Return to Beat | Verdict |
|---|---|---|---|
| 3.0% | 3.0% guaranteed | >3% expected (easily met) | Invest — market likely wins |
| 4.5% | 4.5% guaranteed | >4.5% expected (usually met) | Invest — but closer |
| 5.5% | 5.5% guaranteed | >5.5% expected (uncertain) | Toss-up — depends on risk tolerance |
| 6.5% | 6.5% guaranteed | >6.5% expected (not certain) | Extra payments competitive or better |
| 7.5% | 7.5% guaranteed | >7.5% expected (historical edge) | Extra payments very competitive |
| 8.5%+ | 8.5%+ guaranteed | >8.5% expected (difficult) | Extra payments likely win on risk-adjusted basis |
In 2021, millions refinanced to 2.75–3.25% mortgages. For those homeowners, investing almost certainly beats extra payments. For 2022–2024 buyers at 6.5–7.5%, extra payments are very competitive with investing. The right choice depends entirely on which group you’re in.
Tax-Adjusted Comparison
The comparison must account for taxes: (1) Mortgage interest is potentially deductible if you itemize (reduces effective mortgage rate). (2) Investment gains in taxable accounts are subject to capital gains taxes (reduces effective investment return). (3) Investment gains in 401k/IRA are tax-deferred or tax-free — significantly improving the investment-side math. For investors using pre-tax retirement accounts, the tax advantage of investing significantly tilts the decision toward investing over extra mortgage payments at most rate levels.
Tax-adjusted extra payment vs. Roth IRA investing comparison
| Scenario | Effective Mortgage Rate | Effective Investment Return (Roth IRA) | Decision |
|---|---|---|---|
| 6.5% mortgage / 22% bracket / no itemize | 6.5% | 7–10% long-term (tax-free) | Roth IRA wins |
| 6.5% mortgage / 32% bracket / itemizes | 6.5% × 0.68 = 4.42% | 7–10% long-term (tax-free) | Roth IRA wins more clearly |
| 7.5% mortgage / 24% bracket / no itemize | 7.5% | 7–10% long-term (tax-free) | Very close — risk tolerance decides |
| 7.5% mortgage / 12% bracket / no itemize | 7.5% | 7–10% long-term (tax-free) | Slight edge to investing, but mortgage guarantee has value |
The Non-Mathematical Factors
Beyond the math: peace of mind from mortgage payoff has real psychological value that does not appear in spreadsheets. The risk of job loss, disability, or income disruption is dramatically reduced by owning your home outright. For homeowners within 10 years of retirement, mortgage payoff provides a certain income reduction (no mortgage payment in retirement) that is more reliable than investment returns. For younger homeowners with 30+ year investment horizons, investing in a diversified portfolio at maximum contribution rates typically wins mathematically.
Calculate the Interest Savings Side of the Equation
See exactly how much extra mortgage payments save in interest — then compare this to your projected investment returns to make an informed decision.