Compound interest can be an important tool in structuring a sound financial life. However, compound interest on credit cards can be your worst enemy in trying to survive and get ahead.
Continuing from Part 1, we will focus on the real cost of buying groceries on credit. The information here will demonstrate the adverse effects of using credit and give you weapons you can use in the daily battle against rising prices.
Did you miss Part 1? Read it here first.
Compound Interest
Understanding compound interest is one of the most important concepts in reaching goals such as retirement, funding education, buying a home, or any other financial aspiration.
Here is how compound interest works. Let’s assume you have saved $100. You could stuff it under your mattress, put it in a piggy bank, or bury it in your backyard. If you are disciplined and do not spend it, you can retrieve it in a year, and you will still have $100. However, you want that $100 to grow. So, let’s say you put the $100 in an investment that pays 10% interest. (Actual interest rates on high-yield savings accounts and one-year CDs are around 4%.) A year later, the $100 has grown to $110. A year after that, the $110 has become $121. In 10 years, your $100 would grow to $259.37.
Credit Cards & Compound Interest
Compound interest looks really good if you are investing, right? But if you are paying compound interest, it is a different story. Instead of investing and making money, you are paying and losing money. In addition, the interest rate on credit cards is much higher than interest on conventional investments.
“The higher interest cost is a major factor. On a credit card with a 20% interest rate, that effectively means you are paying 20% more for every purchase you make and can’t pay off,” Austin Kilgore told SavingAdvice. He is an analyst with the Achieve Center for Consumer Insights.
Credit Card Interest on Groceries for a Family of Four
To gauge the financial impact of buying groceries on credit and not paying the balance, let's run some numbers. The average family of four spends between $1,013 and $1,675 a month on groceries, according to the U.S. Department of Agriculture. That averages out to $1,344.
If you buy $1,344 of groceries and do not pay that balance for a month, your bill will grow by $27.53 to $1,371.53. In other words, you have increased your cost by $27.53. That may not seem like a lot if you are in a temporary bind. However, credit cards accumulate interest daily if you carry a balance. So, continuing to carry a balance on that original $1,344 grocery purchase causes the total debt to keep growing.
If you skipped the first monthly payment and then paid $250 a month, it would take you seven months to pay for those groceries. In total, you would have paid $1,470.03 for $1,344 worth of groceries. Your interest payment would total $126.03. Below is a chart showing the monthly breakdown of your payments, interest accrued, and remaining balance based on a standard 30-day billing cycle:
Step-by-Step Payoff Timeline
| Month | Payment Amount | Interest Charged | Remaining Balance |
| Month 1 | $0.00 (Skipped) | $27.53 | $1,371.53 |
| Month 2 | $250.00 (First) | $28.09 | $1,149.62 |
| Month 3 | $250.00 | $23.55 | $923.17 |
| Month 4 | $250.00 | $18.91 | $692.08 |
| Month 5 | $250.00 | $14.18 | $456.26 |
| Month 6 | $250.00 | $9.35 | $215.61 |
| Month 7 | $220.03 (Final) | $4.42 | $0.00 |
Here is How the Math Works if You Carry a Balance for One Month
Credit cards calculate interest daily using your Annual Percentage Rate (APR). Here is how a standard 30-day billing cycle breaks down for a $1,344 charge on a card with a 24.92% APR:
- Daily Interest Rate: 24.92% APR ÷ 365 days = 0.06827% per day
- Daily Interest Charge: 0.06827% of $1,344 = $0.9175 per day
- 30-Day Total: $0.9175 × 30 days = $27.53
The Minimum Payment Trap
Now, let’s look at the impact of making the minimum monthly payment on a credit card with 24.92% interest. This time, we will use figures for a retired couple.
Households with a reference person age 65 or older spent an average of $5,251 on food at home in 2024, or about $437.58 per month, according to Bureau of Labor Statistics data available through the Federal Reserve Bank of St. Louis. Grocery prices have skyrocketed in the year and a half since those figures were tabulated. However, for our illustration, we will use the St. Louis Fed’s number.
It will take 22 months to completely pay off your $437.58 credit card debt if you make only the minimum payment each month. That means you will have paid $549.46 for your $437.58 bill, including $111.88 in accrued interest.
Because your starting balance is low, your monthly minimum payment will probably be $25.00. That is usually the lowest payment available.
The table below illustrates exactly how your balance decreases over time when making the $25.00 minimum payment:
Track the Payoff Schedule
| Month | Starting Balance | Interest Charged | Minimum Payment | Remaining Principal |
| Month 1 | $437.58 | $9.09 | $25.00 | $421.67 |
| Month 2 | $421.67 | $8.76 | $25.00 | $405.43 |
| Month 3 | $405.43 | $8.42 | $25.00 | $388.85 |
| Month 4 | $388.85 | $8.08 | $25.00 | $371.93 |
| Month 5 | $371.93 | $7.72 | $25.00 | $354.65 |
| Month 6 | $354.65 | $7.36 | $25.00 | $337.01 |
| Month 7 | $337.01 | $7.00 | $25.00 | $319.01 |
| Month 8 | $319.01 | $6.62 | $25.00 | $300.63 |
| Month 9 | $300.63 | $6.24 | $25.00 | $281.87 |
| Month 10 | $281.87 | $5.85 | $25.00 | $262.72 |
| Month 11 | $262.72 | $5.46 | $25.00 | $243.18 |
| Month 12 | $243.18 | $5.05 | $25.00 | $223.23 |
| Month 13 | $223.23 | $4.64 | $25.00 | $202.87 |
| Month 14 | $202.87 | $4.21 | $25.00 | $182.08 |
| Month 15 | $182.08 | $3.78 | $25.00 | $160.86 |
| Month 16 | $160.86 | $3.34 | $25.00 | $139.20 |
| Month 17 | $139.20 | $2.89 | $25.00 | $117.09 |
| Month 18 | $117.09 | $2.43 | $25.00 | $94.52 |
| Month 19 | $94.52 | $1.96 | $25.00 | $71.48 |
| Month 20 | $71.48 | $1.48 | $25.00 | $47.96 |
| Month 21 | $47.96 | $1.00 | $25.00 | $23.96 |
| Month 22 | $23.96 | $0.50 | $24.46 | $0.00 |
Immediate Consequences of Buying Groceries on Credit
“Many people are technically current on all of their bills, so they think they are doing okay financially. But, too many people are only making the minimum payment on the credit card, using those credit cards for living expenses, while struggling to pay all the regular expenses,” Ashley Morgan, Ashley F. Morgan Law, tells SavingAdvice. “By only paying minimums on the credit cards and continuing to use the credit cards, it is a sign that your budget is overextended. Being current on your bills does not necessarily mean your financial plan is working.”
Making minimum payments means you continue to carry a balance with these consequences.
- Grace Period Lost: You will lose your interest-free grace period on all new purchases until you pay the entire statement balance down to $0.
- Next Month's Interest: Any new purchases you make next month (like groceries) will begin accumulating interest on the exact day you buy them, rather than at the end of the month.
Managing Credit Card Debt
Credit card debt can be overwhelming. However, if you are in that position, you have options. The experts we talked to in Part 1 of this series all emphasized the need to set a budget.
A classic budget takes monthly income and subtracts the bare necessities, such as housing, food, utilities, and medical costs. Once you have done that, you can chip away at debt.
If you are trapped in a cycle, Morgan suggests you stop buying groceries on credit—whether that means putting away credit cards, Buy Now, Pay Later offers, or personal loans.
“Groceries get eaten, and the debt does not.” Lifestyle Creator Janiece Okpobiri tells SavingAdvice. “You end up paying interest on food that is already gone, which means next month's grocery money is a little less money than this month's was. That is the mechanism that turns one hard month into a pattern, and it is the same trap I watched people fall into with buy now pay later.”
You May Get Relief
It may seem natural to think of a credit card company or lender you owe money to as your enemy, but they can be your ally. Before missing a payment, reach out to see if they have a temporary hardship program or can lower interest rates.
There are also certified credit counseling agencies that may be able to help structure a debt management plan. So, you haven't run out of options.
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