FREE CALCULATOR · MONEY

Payoff vs Invest Calculator

Extra cash, two good uses. Run your debt's APR against your expected investment return and see which choice leaves you richer — the internet's most-asked money question, answered with your numbers.

Pay off debt or invest?

Enter what you could put toward either path each month. The calculator compounds the same dollars both ways — as guaranteed debt savings and as invested growth — and tips the scale toward the winner.

How it works: your monthly amount is compounded twice — once at your debt APR (the guaranteed return, since each dollar of principal retired stops costing you that rate) and once at your expected investment return. Whichever future value is higher wins; the beam, the chart, and the verdict all read off the same two numbers. Taxes are not modeled — see the FAQ for the real-world adjustments.

How the payoff-vs-invest math works

The whole question reduces to one comparison: two rates. Paying down a loan at 7% APR is economically identical to earning a guaranteed 7% — the interest you stop paying is money you keep, on a schedule you can compute to the cent. Investing at an expected 8% might earn more, but "expected" is doing real work in that sentence. The calculator runs the same monthly dollars through both rates over your horizon and shows you the dollar difference.

The formula

gain = E × ((1 + r/12)^12×T − 1) ÷ (r/12) where E = monthly amount, T = years · run once with r = debt APR, once with r = expected return · crossover: investing wins only if expected return > debt APR

This is the future value of a monthly savings stream — the standard way to compare what recurring dollars become. Because both paths start with the same dollars, everything except the two rates cancels out, which is why the crossover is exactly your debt's APR.

Worked example

$500 a month for 10 years, against a 7% debt or invested at 8%:

1. Pay the debt: 500 × ((1 + 0.07/12)¹²⁰ − 1) ÷ (0.07/12) = $86,542.40 of guaranteed gain.

2. Invest it: 500 × ((1 + 0.08/12)¹²⁰ − 1) ÷ (0.08/12) = $91,473.02 of expected gain.

3. The difference: $91,473.02 − $86,542.40 = $4,930.61 to investing.

4. The crossover check: drop the expected return to 6% and the debt path wins by about $5,800 — flip the return above 7% and investing takes the lead. The scale tips exactly at the debt's APR.

Where this comes in handy

High-interest debt check: at 20%+ APRs, almost nothing beats paying the debt down — confirm it with your card's actual rate.
Windfall routing: bonus, refund, or inheritance — run the comparison once, then commit instead of agonizing.
Low-rate mortgage sanity check: at a 3–4% mortgage rate, the market usually wins on paper — the pay off debt or invest guide covers when that is (and is not) smart.
Risk-appetite reality check: the investing number assumes a steady return; if you want the guaranteed outcome, the debt column is the honest one.

Payoff vs invest — frequently asked questions

What is the "guaranteed return" of paying off debt?

Every extra dollar of principal stops accruing interest at your APR, so paying down a 7% loan is like earning a risk-free 7% on that dollar — no market can take it back. The calculator compounds your monthly dollars at your debt rate to show that guaranteed gain, side by side with the expected (not guaranteed) investment gain.

At what return does investing beat paying off debt?

Exactly at your debt's APR — that is the crossover. Investing needs to earn more than the debt costs for the investing path to come out ahead. In the default example, 8% beats the 7% debt; drop the expected return below 7% and the scale tips back to the debt. Try your own numbers: the crossover never moves off the APR.

Does this calculator account for taxes?

It compares headline rates. In real life, mortgage interest may be tax-deductible (which lowers your effective debt rate) while investment gains face capital gains tax (which lowers your effective return) — and both adjustments favor paying down debt slightly. Treat the calculator's result as the starting point, then check your tax situation for the fine print.

What if my debt is a 0% balance transfer or a cheap mortgage?

Then paying it off has a near-zero guaranteed return, and almost any positive investment return wins. This is the one case where the answer is nearly always "invest" — plug in your numbers and watch the beam swing hard toward the investing pan.

Should I skip investing to kill debt even with a 401(k) match?

No — capture the full employer match first. A 50–100% instant match beats every debt rate on this page. Fund the match, then run this comparison with whatever is left over.

What about my emergency fund?

Keep a starter cushion — roughly one month of expenses — before either path, then build toward 3–6 months alongside whichever strategy wins. An emergency charged to a 24% card undoes months of either plan.

How does this compare with the debt payoff comparison calculator?

That tool (debt payoff comparison calculator) compares payoff strategies against each other — snowball vs. avalanche vs. minimums. This page answers a different question: whether the extra dollars should go to debt at all, or into the market. Use them together — this one picks the destination, that one plans the attack. The compound growth calculator shows what the investing path looks like stretched over decades.