Pay off debt or invest? Compare the rates

Paying off debt earns a known return equal to its rate; investing does not. Compare a credit card with a low-rate loan using plain arithmetic.

Part of the Start Here: Money Basics track on Agenticks. About 9 minutes, written for a beginner reader.

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Key takeaways

Should spare money go toward debt or into investments? It sounds like a matter of opinion, but most of it is arithmetic. Every unit of debt you pay off earns a return equal to that debt's interest rate, because that is the interest you no longer pay. An investment might earn more or less than that, and you only find out afterwards. So the decision comes down to comparing a known number with an uncertain one. This lesson works through that comparison for a high-interest credit card and a low-rate loan, explains why an employer's matching contribution is a special case, and shows a common way to order several debts. It assumes you already have at least a small emergency fund, so paying down debt does not leave you one surprise away from borrowing again.

Paying off debt is a return you can count on Suppose you owe 1,000 on a card charging 20% a year. Leave it, and it costs about 200 in interest over a year, a little more because card interest is usually charged monthly. Pay it off, and that cost disappears. A year later you are about 200 better off than if you had left the balance, exactly as if you had invested 1,000 and earned 20%. The difference is risk. The 200 saved is certain. A 20% gain from investing is not: broad share markets have had years far better than that and years far worse, and nobody knows in advance which kind of year is coming. The SEC's investor guidance is direct: no investment strategy pays off as well as, or with less risk than, paying off all high-interest debt. An unpaid balance also grows the same way savings do under compounding, only against you, as interest is charged on earlier interest. That is also why the CFPB describes paying the highest-rate debt first as the approach that targets the debt costing you the most. To compare, find the annual percentage rate (APR) on each debt: the yearly cost of borrowing as a percentage, which in many countries also includes certain fees. It is printed on your statement or loan agreement.

Known versus uncertain

A debt payment's return is the interest rate: fixed and certain. An investment's return is a range of possible outcomes. When the certain number is high, as with most credit cards, it is hard for anything uncertain to compete. When it is low, reasonable people land on different sides.

Worked example: a 20% card and a 4% loan

You have 2,000 spare, in any currency. You owe 2,000 on a credit card at 20% a year and 10,000 on a car loan at 4%. For illustration only, investing is assumed to average 5% a year, with no promise for any single year.

Put 2,000 toward the card (2,000 x 20%, certain)about 400 a year saved
Put 2,000 toward the car loan (2,000 x 4%, certain)about 80 a year saved
Invest the 2,000 (2,000 x 5%, uncertain and could be negative)about 100 a year on average
Card compared with investing (400 - 100, and the card's 400 carries no market risk)about 300 a year in favour of the card
Loan compared with investing (100 - 80, and only if the assumed 5% shows up)about 20 a year in favour of investing, on average
What the arithmetic saysThe card wins clearly; the low-rate loan is close to a coin toss

Illustrative round numbers. Interest is shown as simple yearly figures; monthly charging makes the card's cost slightly higher. Tax can change the comparison in some cases.

Low-rate debt is a judgement call When a debt's rate is low, the comparison stops being one-sided. In the example, the loan costs 4% and investing is assumed to average 5%: a gap of one percentage point that may or may not appear, and that disappears entirely in a bad year. Reasonable people land on either side: Paying the low-rate debt off faster gives a certain return, frees up the monthly payment sooner, and brings peace of mind, which has real value. Investing instead, while paying the debt on schedule, gives the money longer to compound, may come out ahead over many years, and keeps the money in assets you can still sell, rather than in a paid-off loan you cannot get back. Some details tip the balance. Interest on certain debts is tax-deductible in some countries, which lowers its true cost. Some loans charge a penalty for paying early. Variable rates can rise. And money paid into tax-advantaged accounts can come with tax relief that changes the comparison. Those rules depend on where you live and on your situation; the Accounts and Tax track explains them by country.

Employer matching: a special case Many workplace retirement plans add money when you contribute. In a typical arrangement the employer puts in a set amount for every unit you contribute, up to a limit, for example 50 cents for each 1 you pay in, on contributions up to 5% of salary. That match is an immediate return on your contribution before any investment growth: in this example, 50% on the day it arrives. The SEC puts it this way: not contributing enough to get your employer's maximum match means passing up free money for retirement. That is why many people contribute enough to receive the full match even while paying down debt, and send money beyond the match to their debts. Matching rules differ a great deal. Some employers require you to stay a set number of years before the matched money is fully yours, which is called vesting, and the plans themselves differ by country, from workplace pensions in the UK to group retirement plans in Canada and 401(k) plans in the US. The plan's own documents set out its rules, and the Accounts and Tax track covers how each country's accounts work.

An employer adds 50 cents for every 1 you contribute, on contributions up to 5% of salary. On a salary of 40,000, contributing 5% brings how much from the employer? 1,000 5% of 40,000 is 2,000, and half of 2,000 is 1,000.

Ordering several debts With more than one debt, a common approach is to pay the minimum on every debt, then send every spare amount to the one with the highest interest rate. Once it is cleared, the money moves to the next highest. This is often called the debt avalanche, and it costs the least interest overall. The CFPB describes it alongside the debt snowball, which clears the smallest balance first for quicker wins, and notes that the snowball may cost more in the long run. If the quick wins are what keep you going, that trade-off can be worth it: a plan you stick to does more than a cheaper plan you abandon. Either way, the budgeting lesson shows where the monthly amount comes from, and once the expensive debts are gone, the same payment can turn into the monthly investment described in how to start investing.

The debt avalanche pays the highest rate first. Put these debts in avalanche order, first to last.

  1. Store card at 30% APR
  2. Credit card at 22% APR
  3. Personal loan at 9% APR
  4. Car loan at 5% APR
  5. Mortgage at 4% APR

You can compare debt and investing

You can now turn a debt's rate into a known return, compare it with an uncertain investment return, explain why an employer match is a special case, and order several debts by the avalanche method.

Check your understanding

You pay off 1,500 of a card balance charging 18% a year. Roughly what is that worth over a year?
About 270 in interest you no longer pay, with certainty. Right. 1,500 x 18% is 270, and the saving does not depend on markets. Monthly charging makes it slightly more.
Why is a 4% loan a closer call than a 20% credit card?
An uncertain investment return could plausibly beat 4%, but rarely beats 20% reliably. Yes. The lower the debt's rate, the more room an uncertain investment has to come out ahead.
In the debt avalanche method, which debt gets the extra payments first?
The one with the highest interest rate. Correct. Paying the most expensive debt first keeps total interest as low as possible.
Why is an employer match treated as a special case?
It adds an immediate return on what you contribute, before any investment growth. Exactly. A match of 50 cents per 1 contributed is a 50% return on the day it arrives, subject to the plan's rules.

Common questions

Is it better to pay off debt or invest?
Compare the debt's interest rate with the return an investment might earn. Paying off debt earns its rate with certainty; investing is uncertain. High-interest debt usually wins that comparison clearly, while low-rate debt is a closer call that depends on the details.
Should I pay off my credit card before investing?
US regulators say no investment strategy pays off as well as, or with less risk than, paying off high-interest debt. A card charging around 20% a year is far above what investments can be relied on to earn.
Should I take my employer match if I have debt?
An employer match is an immediate return on your contribution, which is why many people contribute enough to receive the full match even while paying down debt. Plan rules differ, including vesting periods, so the plan's own documents are the place to check.

Terms defined in this lesson

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Written and reviewed by the Agenticks Learn editorial team. How we write and check lessons.

Agenticks Learn is general education. It is not financial, investment, tax or legal advice, it does not take your situation into account, and nothing on it is a recommendation to buy, sell or hold any security or to open any account. Examples use illustrative numbers. Investing involves risk, including losing money you put in, and past performance does not predict future results. Tax rules and limits change; the official sources linked in each lesson are the final word.