Pay Off Debt or Invest? The Rate Test, With Math

Short answer: Compare the interest rate on the debt with the return you could realistically expect from investing. Every dollar you put toward a 22% credit card earns a guaranteed 22%, which no investment reliably beats, so pay that off first. A debt near 8% is close to a tie with a hypothetical 8% return, and a low-rate debt around 4% usually lets investing come out ahead, though that gain is not guaranteed. One exception: grab any employer 401(k) match first. Educational content only. Not financial advice.

The question sounds like a values debate, but most of it is arithmetic. Paying off a debt early is a risk-free return equal to its interest rate. Investing has a higher expected return over long periods, with no promise. Put both on the same timeline and the answer usually falls out.

The rate test

Use the debt’s interest rate as the bar an investment has to clear:

Debt rate	Typical example	Usual call
Above about 8%	Credit cards, personal loans	Pay it off first. The guaranteed return beats a hypothetical market return.
About 6% to 8%	Many car loans, some student loans	Close call. Split extra money, or lean toward paying it off if you want certainty.
Below about 5%	Older mortgages, low-rate student loans	Investing usually wins on paper, as long as the payment is comfortable.

These bands line up with common guidance: Fidelity suggests that if your debt’s interest rate is 6% or higher, you should generally pay it down before investing extra money for retirement. For scale, the Federal Reserve reports that credit card accounts charged interest averaged 22.36% in August 2026, and 60-month new car loans at banks averaged 7.54%.

Worked example: $15,000 of debt and $300 a month extra

You owe $15,000 on a 5-year (60-month) payoff plan and have an extra $300 a month. Two choices, compared at the end of the same 5 years:

• Debt first: add the $300 to the payment until the debt is gone, then invest the whole payment plus the $300 every month.
• Invest now: make the regular payment for 60 months and invest the $300 every month from day one.

Investments earn a hypothetical 8% a year, compounded monthly. Both plans end debt free at month 60, so the investment balance is the whole score:

Debt rate	Regular payment	Debt first: paid off	Interest saved	Debt first: invested at 5 y	Invest now: invested at 5 y	Winner
22%	$414.28	Month 27	$5,742	$26,481	$22,043	Debt first, by $4,438
8%	$304.15	Month 28	$1,796	$22,043	$22,043	Exact tie
4%	$276.25	Month 28	$858	$20,995	$22,043	Invest now, by $1,048

Look at the middle row. When the debt rate equals the investment return, the two plans land on the same dollar. That is the whole rate test in one line. At 22% the card costs far more than the market is likely to pay, so killing it first leaves you $4,438 ahead. At 4% investing comes out about $1,048 ahead, but only if the hypothetical 8% shows up; the $858 of interest saved by paying early is certain.

The invest-now column is simply $300 a month for 60 months at 8%. Check it in the compound interest calculator, then try your own rate and amount.

Assumptions: fixed-rate debt on a 60-month amortized plan, payments and deposits at the end of each month, a constant hypothetical 8% return compounded monthly, before taxes and fees. Examples are hypothetical, not guaranteed.

Three things that change the answer

• An employer match. A match is an instant return on your contribution. If your employer adds 50 cents per dollar on the first 6% of a $60,000 salary, putting in $3,600 a year brings $1,800 of free money. Get the full match even while paying off a card; here is how the match fits the 401(k) limits.
• No emergency fund. Without cash for a surprise bill, the next emergency goes right back on the card. Build a starter cushion first, kept somewhere that pays interest; see how high yield savings accounts work.
• Taxes and the kind of debt. Interest on some student loans and mortgages can be tax deductible, which lowers the real rate a little, while investment gains in a taxable account are taxed. Federal student loans also have repayment options most debts do not; see how long it takes to pay off student debt.

A simple order that works for most people

1. Pay every minimum on time.
2. Build a small emergency fund.
3. Collect the full employer match.
4. Pay off debt above about 8%, highest rate first.
5. Split extra money on debt between 5% and 8%, or pick the side that lets you sleep.
6. Invest the rest and pay low-rate debt on schedule.

If you have several debts and want to see two payoff orders race each other, our video I Paid Off $18K Two Ways runs the numbers. And once the debt is gone and you are living on savings, see how long your savings will last.

Educational content only. Not financial advice. Examples are hypothetical, not guaranteed. Returns are not guaranteed and past market performance does not predict future results. Tax rules vary; check with a tax professional for your situation.

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