Should You Pay Off Debt or Invest the Extra Money?

The simple rule — and why it's not enough

The standard advice is: if your debt interest rate is higher than your expected investment return, pay the debt. If lower, invest. This is correct as far as it goes — but it ignores taxes, risk, and the psychological reality that debt carries stress that investments don't.

Historically, the S&P 500 has returned about 10% annually before inflation, or about 7% real. So the rough threshold is: debt above 7% should be paid off first; debt below 7% can potentially be invested alongside. But tax-advantaged accounts (401k, IRA) change the effective return, and mortgage interest is tax-deductible for many filers, which changes the effective rate.

Let's break it down by debt type, because the decision is very different for a 3% mortgage and a 22% credit card.

Credit card debt: always pay this first

Credit card APRs average 20–24% (2024). No investment reliably returns 20%+ after taxes. If you carry a $5,000 balance at 22% and pay $200/month, it takes 33 months to pay off and costs $1,485 in interest. If you invest that $200/month instead at 7%, you'd earn about $230 over the same period — but you'd still owe $5,000 at 22%, accruing $917 in interest during those 33 months.

The math is unambiguous: pay credit cards first. The 22% interest is guaranteed and risk-free (you save 22% for certain); the investment return is uncertain and taxed.

Our credit card payoff calculator shows exactly how long it takes and how much interest you save by paying more.

Mortgage at 7%: the borderline case

A 7% mortgage is right at the threshold of the stock market's historical real return. At 7%, a $300,000/30-year loan costs $1,996/month and $418,607 total interest. If you pay an extra $200/month, you finish in ~22 years and save ~$120,000 in interest.

Alternatively, invest $200/month at 7% for 30 years: $243,429. That's more than the $120,000 interest savings — but only if you actually earn 7% consistently for 30 years, which is not guaranteed. The mortgage payoff is a guaranteed 7% return (every dollar of principal saves 7% of interest for certain).

If your mortgage is tax-deductible and you're in the 22% bracket, the effective rate is 7% × (1 − 0.22) = 5.46%. That's below the 7% market return, making investing mathematically better. But the mortgage payoff is risk-free, and the investment return is not. The risk premium matters.

Use the mortgage calculator to see your exact interest savings from extra payments, then compare to the investment calculator's projected growth.

Student loans: depends on the rate

Federal student loans for 2024 carry rates of 5.5–8.5% depending on the loan type and year. Private loans can be higher. At 5.5%, investing is likely better — the market's 7% historical return exceeds the loan cost, and student loan interest is partially tax-deductible (up to $2,500/year), reducing the effective rate further.

At 8.5%, the calculus shifts. Paying down the loan gives a guaranteed 8.5% return, which beats the market's 7% real return. And unlike mortgage interest, student loan interest is only deductible up to $2,500 and phases out at higher incomes.

The student loan calculator can show you the total interest at your rate, and the ROI calculator can show what investing the same amount would yield.

The 401(k) match — always take it

There's one exception to every debt-first rule: if your employer matches 401(k) contributions, that's free money. A 50% match on 6% of salary is an immediate 50% return. No debt interest rate — not even a 24% credit card — beats a 50% instant, guaranteed return.

On an $85,000 salary, contributing 6% ($5,100/year) with a 50% match = $2,550 in free money. Even if you have credit card debt, contribute enough to get the full match first, then put everything else toward the debt.

After the match is captured, prioritize debt by interest rate: credit cards first, then personal loans, then student loans, then mortgage. The 401(k) match is the only investment that beats all debt payoff.

The psychological factor

The math might say invest at 7% instead of paying a 5% mortgage. But debt carries psychological weight that investments don't. A paid-off mortgage means security — if you lose your job, the housing cost disappears (except for tax and insurance). An investment portfolio can drop 30% in a market crash, right when you might need it.

Many financial advisors recommend a hybrid approach: max the employer match, pay off all non-mortgage debt, then split extra money between mortgage prepayment and investing. This balances the math with the peace of mind.

The ROI calculator lets you see what a given investment amount would grow to — but remember that past performance doesn't guarantee future returns, and the mortgage payoff is a sure thing.