Pay off debt or invest?

Compare your interest rate against expected market returns — with the honest breakeven and when each wins.

The math is simpler than it feels. Paying off a debt gives you a guaranteed, tax-free return equal to its interest rate. Investing gives you an uncertain return that has historically averaged around 7% a year in real terms for a diversified stock portfolio. So the core question is just this: is your debt's interest rate higher or lower than what you could reasonably expect to earn in the market?

But before you weigh that trade-off at all, put two things ahead of both: a small emergency fund of a few thousand dollars so a surprise doesn't send you back to the credit card, and — if your employer offers one — enough into your 401(k) to capture the full match. The match is the single best return available to you: a dollar-for-dollar or fifty-cent match is an instant 50–100% return, which beats paying off even a 22% credit card. Never leave it on the table to do anything else.

After that, high-interest debt wins almost every time. A credit card at 22% is a 22% guaranteed, tax-free return if you pay it off, and no investment reliably clears that bar. Attack it before you invest another dollar — the credit-card payoff calculator shows just how much interest a lingering balance really costs. A car loan or personal loan in the low-teens is usually worth prioritising too.

Low-interest debt is where it gets genuinely interesting. A student loan at 4–5% or a mortgage at 6% sits below the long-run expected return of stocks, so mathematically, investing the difference is likely to come out ahead over decades. The word doing the heavy lifting is "likely" — the market return is a long-run average wrapped around some genuinely awful years, and the debt's return is certain.

Here's the size of the gap. Suppose you have $10,000 spare and a 4% student loan. Paying it down saves you a guaranteed 4%. Investing it instead, at a 7% real return, could grow to roughly $19,000 over ten years versus about $4,900 of interest avoided — you can model either path with the compound-interest calculator. The expected edge is real, but so is the risk, and it only shows up if you actually invest the money rather than spend it.

That's why the honest answer bends toward temperament as much as arithmetic. If carrying any debt keeps you up at night, the guaranteed return of paying it off buys something a spreadsheet can't price: peace of mind and a simpler balance sheet. If you can genuinely tolerate the volatility and leave the money invested through a downturn, the low-interest-debt-plus-investing route usually wins on paper. Neither choice is wrong when the rates are close.

One more nuance: money inside a tax-advantaged account grows shielded from tax, which quietly tilts the maths toward investing for anything beyond high-interest debt — the same logic behind the Roth-vs-Traditional decision. Once your plan is set, run your actual balances through the debt-payoff calculator to see a real payoff date, and check how that timeline feeds your bigger picture in when can I actually retire.