Pay Off Mortgage or Invest Calculator
| Mortgage rate | Guaranteed return if prepaid | Invest 7% wins when |
|---|---|---|
| 3% | 3% risk-free | almost always |
| 4.5% | 4.5% risk-free | close call |
| 6.5% | 6.5% risk-free | usually payoff |
| 8%+ | 8% risk-free | payoff, clearly |
The extra-cash duel has a clean mathematical frame: paying down a mortgage is a GUARANTEED, tax-free return equal to your interest rate - prepaying a 6.5% loan is 'earning' 6.5% risk-free, which no savings account matches. Investing is an EXPECTED return - 7% is the long-run stock market average before inflation and taxes, but it arrives lumpy and can lose 30% in a bad decade. The raw comparison is your mortgage rate versus your expected after-tax return: above roughly 6-7%, the guaranteed payoff usually wins; below 4-5%, the math usually favors investing; in between, it is genuinely close.
The decision is not only arithmetic, and pretending otherwise is how bad advice gets given. Payoff buys certainty, lower required cash flow, and the psychological weight of owning your home; investing buys liquidity (a paid-off house cannot pay an emergency bill), diversification, and higher expected long-run wealth. The professional caveat that outranks everything: 401(k) match dollars are an instant 50-100% return - capture the full match BEFORE either choice, and kill any credit-card debt (20%+) before both.
How to use
- Enter your loan balance, rate, remaining term, and the extra monthly amount you are deciding about.
- Enter the investment return you would realistically earn (7% is the long-run stock average; subtract taxes for taxable accounts).
- Read both endgames side by side: interest saved and years cut by payoff, versus projected portfolio value by the same date - then read the honesty note about which comparison actually applies to you.
Frequently asked questions
Is it better to pay off the mortgage or invest?
Compare rates: mortgage above about 6% usually favors payoff (a guaranteed, tax-free 6%), below about 4.5% usually favors investing (the market's long-run 7% expected beats cheap debt). Between those, it is close enough that certainty, cash-flow relief and sleep quality are legitimate tiebreakers - the calculator shows both endgames so the tiebreak is informed.
Why is paying off debt called a guaranteed return?
Every dollar of principal prepaid eliminates an entire future interest stream at your loan's rate, with zero risk and zero tax (up to deduction limits, mortgage interest is mostly not deductible anymore at high standard deductions). A 6.5% mortgage payoff is therefore a 6.5% risk-free after-tax return - better than any CD or treasury at normal rates.
What about liquidity - why does it matter?
Home equity is trapped: it cannot pay an emergency bill without a HELOC application or a sale. Investments can be sold in days. The standard sequencing respects that order - emergency fund first, employer match second, high-interest debt third, and only then the mortgage-versus-invest duel with money you will not need soon.
Does the answer change if I plan to move?
Yes, materially: prepaying a mortgage you will sell in 3 years earns that guaranteed return only until you sell, and the equity is recycled into the next house's down payment either way. Short horizons weaken the payoff case (fewer years of guaranteed interest saved) and make liquid investing relatively more attractive - the calculator's year count shows exactly how much runway each plan buys.