I get asked this at least once a week. Someone has $10,000 in credit card debt at 22% and $5,000 in savings. They want to know if they should put the $5,000 toward debt or put it in the stock market. Or maybe they have a mortgage at 4% and an extra $500 a month. Should they pay extra on the house or fund their Roth IRA?
The answer is not “always debt” or “always invest.” That’s lazy advice. The answer depends on the interest rate, your risk tolerance, and your psychology.
Let me tell you about two people I worked with.
First, a guy named Paul. He had $8,000 on a credit card at 24%. He also had $3,000 in a savings account earning 1%. He asked me if he should invest the $3,000. I said “no, pay the card.” He said “but I might miss out on stock market gains.” I said “the stock market averages 10% before taxes. Your credit card is costing you 24% guaranteed. Paying it off is a 24% return with zero risk. You cannot beat that.”
Paul paid off $3,000 of the card. His interest dropped by about $60 a month. He said “I didn’t realize paying debt was like investing in a guaranteed 24% return.” He finished the rest of the card in six months.
Second, a woman named Sarah. She had a mortgage at 3.5% and a car loan at 0.9% (promo rate). She had an extra $500 a month. She asked if she should pay extra on the mortgage or invest in a low-cost index fund. I said “invest.” She said “but Dave Ramsey says to pay off the mortgage.” I said “Dave Ramsey’s advice is for people who can’t do math. Your mortgage costs you 3.5% after taxes maybe 2.5%. An index fund historically returns 8-10%. You’re leaving money on the table by paying the mortgage early.”
She invested the $500 a month. Over five years, that grew to about $38,000. If she had paid extra on the mortgage, she would have saved about $4,000 in interest. The difference was $34,000. That’s not a small difference.
So here’s the rule. Compare the interest rate on your debt to the after-tax expected return on your investments. If the debt rate is higher, pay it down. If the investment return is higher, invest.
But there’s a catch. Investment returns are not guaranteed. Debt interest is guaranteed. So you need to add a risk premium. I use a simple rule: if your debt rate is above 8%, pay it down aggressively. If it’s between 5% and 8%, it’s a toss-up – do whatever helps you sleep. If it’s below 5%, invest.
That’s for after you’ve built an emergency fund and aren’t carrying high-interest credit card debt. Because credit cards at 22% are an emergency. Don’t invest a dollar until those are gone.
Let me show you the math with the extra payment analyzer.
Say you have a $10,000 personal loan at 12%. You have $200 extra a month. If you put that $200 toward the loan, you save about $1,400 in interest and pay it off two years early. That’s a guaranteed 12% return on your $200 monthly investment.
Now say you have a mortgage at 4%. You have $200 extra. If you invest that $200 in the market at 8% average return, after ten years you’d have about $37,000. If you put it toward the mortgage, you’d save about $9,000 in interest. The difference is $28,000. That’s real money.
But – and this is a big but – most people don’t actually invest the extra money. They say they will, but then they spend it on takeout or a new TV. If you’re not disciplined enough to auto-invest, then paying down debt is a better behavioral move. It forces you to improve your balance sheet.
I remember a client named David. He had a 5% car loan and an extra $300 a month. He knew the math said to invest. But he also knew he would probably spend the money if he didn’t lock it away. So he paid extra on the car loan. Was it mathematically optimal? No. Was it better than spending the money on crap? Yes. He paid off the car in three years instead of five. Then he took the old car payment and invested it. That worked for him.
So the math is clear, but the psychology matters.
Now, what about retirement accounts? If your employer offers a 401(k) match, take that first. That’s a 100% return on your contribution. Nothing beats that. Even if you have credit card debt at 24%, put enough into your 401(k) to get the match. Then put everything else toward the debt.
Someone I worked with – let’s call her Lisa – had $15k in credit card debt at 19%. Her employer matched 50% of her 401(k) contributions up to 6% of her salary. She wanted to skip the 401(k) to pay debt faster. I said no. Put in 6%. Get the 3% match – that’s free money. Then throw everything else at the card. She did that. The match alone earned her about $2,000 a year. That more than offset the extra interest on the card.
Use the debt payoff calculator to see how much extra interest you’re paying while you contribute to your 401(k).
In Lisa’s case, the extra interest from delaying debt payoff was about $400 over 18 months. But the 401(k) match gave her $3,000. Net win: $2,600. So don’t skip free money.
One more scenario. What about balance transfers? If you have high-interest debt, a balance transfer to a 0% card can give you a breather. But only if you pay it off before the promo ends. Use the balance transfer calculator to check.
If you can drop your rate from 22% to 0% for 18 months, you could put the money you would have paid in interest toward principal. That’s a huge win. But don’t use the freed-up cash to invest. Use it to kill the debt while the rate is zero.
So here’s my bottom line. Pay off high-interest debt (over 8%) before investing. For medium-interest debt (5-8%), consider your risk tolerance and discipline. For low-interest debt (under 5%), invest, especially if you have a 401(k) match.
But don’t let perfect be the enemy of good. If paying off a 5% loan gives you peace of mind, do it. The goal is progress, not mathematical perfection.
I’ll leave you with this. Run your own numbers. Use the extra payment analyzer to see the impact of paying debt. Then compare it to a simple investment calculator. The difference might surprise you. Then decide.
P.S. Sarah – the one who invested instead of paying her 3.5% mortgage – she just checked her portfolio. It’s up 12% over three years. Her mortgage is still at 3.5%. She’s happy. But she also admits she’s lucky with the timing. If the market had crashed, she’d feel different. That’s the risk.
James Whitfield, Austin
