Debt vs Invest: Which Comes First?
One spare $200 a month, an 18% credit card and a 7% market: should the money kill the debt or buy index funds? Run both futures to the same finish line and compare net worth.
How to use this calculator
Run the numbers once, write the result where you will see it, and let the free expense tracker do the weekly work: it sorts every entry into needs, wants and savings automatically, so drift from the plan is visible the moment it starts instead of at the end of the month. A calculator sets the target; tracking is what actually gets you there.
The honest comparison is net worth
Half the internet argues this question with feelings; the calculator argues it with arithmetic. Both strategies get your same extra monthly amount for the same number of years: pay-debt-first clears the balance, then invests every dollar afterward; invest-first buys funds the whole time while the debt rides at its APR. At the finish line each strategy reports one number — assets minus remaining debt — because dollars in a fund and dollars of debt you do not owe are worth the same at the end, and only net worth compares them fairly.
Paying off debt is a guaranteed return
Killing an 18% APR balance is mathematically identical to earning a risk-free 18% on that money — no investment on earth offers a guaranteed 18%, which is why high-interest debt first is the least controversial advice in finance. The flip side is equally true: extra payments into a 5% mortgage are a guaranteed 5%, and a diversified portfolio has historically averaged more than that. The rate fields are where your actual debate lives — the verdict usually flips somewhere between card debt and mortgage debt.
When investing first genuinely wins
The strategy that sounds wrong — investing while debt survives — wins in two real cases. Low-rate debt: a 4% student loan or mortgage against a market averaging 7% is an arbitrage where the spread compounds for you. Employer money: a 401(k) match is an instant 50-100% return that no debt payoff can match, so the match gets funded before any extra dollar goes anywhere. The calculator’s breakeven row states the boundary precisely: it solves for the investment return at which both futures tie, and your real expected return sits either above or below it.
The variables that move the verdict
Run it three ways before deciding: your debt at its real APR, at half, and at zero — watch how much of the gap is the rate rather than the plan. Then stretch the years field: short horizons favor clearing debt because the market may be down at your finish line, while long horizons let compounding dominate. The number that matters least is the exact expected return — anywhere in the 6 to 8% historical band produces the same verdict for most real debts, and pretending more precision than that is how forecasts get trusted more than they deserve.
Frequently asked questions
Should I grab the employer match before anything?
Yes — a match is an instant guaranteed return bigger than any credit card rate. Fund the match, then let this calculator settle the question for the dollars beyond it.
Is there an emergency cash buffer first?
Keep one month of essentials in cash before extra debt payments, or the next surprise goes back on the very card you are clearing. The buffer is what makes the payoff plan survive contact with a flat tire.
Is this financial advice?
It is arithmetic — the calculator shows what the two strategies do to net worth under the rates you enter. Rates, risk tolerance and tax situations vary; treat the output as the numbers for the debate, not the verdict of a licensed professional.