What Is Debt?
Learn what borrowing means, when debt can help, and when it creates problems.
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Why what is debt matters
Debt means you borrow money today and agree to repay it later, with interest. Interest is the cost of borrowing, the lender charges you extra for the time you have their money.
Most adults have some form of debt. The question isn't whether debt is inherently good or bad, it's whether the value you get from borrowing is worth more than what the borrowing costs.
How interest works
When you borrow money, you pay back the original amount (the principal) plus interest. Interest is usually expressed as an APR (Annual Percentage Rate), the yearly cost of borrowing expressed as a percentage.
$500 borrowed at 18% APR for 12 months:
- Monthly interest rate: 18% ÷ 12 = 1.5%
- Month 1 interest: $500 × 1.5% = $7.50
- If you only pay the minimum (~$10), most of it covers interest, very little reduces the $500
- Total paid over 12 months if you pay only minimums: roughly $550–$570
You borrowed $500 and paid back $550–570. The extra $50–70 is what the borrowing cost you.
Higher APR = higher interest cost. A credit card at 20% APR costs more than a student loan at 5% APR on the same balance.
Useful debt vs costly debt
Some debt creates value greater than its cost. A $10,000 student loan at 5% over 10 years (total cost: ~$12,700) that leads to a career paying $30,000/year more than you'd earn otherwise is worth it, the $2,700 in interest is a small fraction of the benefit. A $500 credit card purchase at 18% APR that you carry for a year on something you no longer own costs $90 in interest for something with zero remaining value. The math matters: what did the borrowing get you, and was that worth the interest cost?
Types of debt
- Credit card: typically 18–25% APR. Meant to be paid monthly to avoid interest. If you carry a balance, interest accumulates fast.
- Student loans: federal loans typically 5–7% APR. For education expected to increase earning potential.
- Auto loan: typically 5–10% APR. For a vehicle, a depreciating asset.
- Mortgage: typically 4–7% APR. For a home, which may appreciate in value.
- Payday loans: often 300–400% APR equivalent. Extremely expensive short-term borrowing, almost always a bad deal.
What changes the outcome
Same person, two choices: Option A borrows $500 on a 20% APR credit card for concert tickets. Carries the balance for 12 months. Paid ~$600 total for something that is over. Option B borrows $500 on the same card for a professional certification course. Carries the balance for 12 months. Paid ~$600 for a qualification that leads to a $3/hour raise. Option A lost $100 to interest on a fading memory. Option B paid $100 in interest for something that generates thousands of dollars in future income. The debt amount was identical. The return on that debt was completely different.
Debt payoff
Minimum only
62 mo
Est. interest: $1,293
Minimum + extra
30 mo
Est. interest: $598
How to think it through
Before taking on any debt, ask:
- What is the APR?
- What is the total I'll pay back (principal + interest)?
- What do I get from borrowing? Does the value of what I get exceed what I pay back?
- Can I afford the monthly payment without disrupting my budget?
If the answer to question 3 is unclear or the answer to question 4 is no, don't borrow.
Signs a debt is a problem:
- APR over 20%
- You're borrowing for things that have already been consumed (food, entertainment, past experiences)
- Monthly payments take more than 15–20% of your net income
- You're borrowing to pay off other debt (debt cycle)
Real-world example
Two classmates both need $300 for a situation they can't cover from savings. Alex puts $300 on a credit card at 22% APR and pays the minimum ($10/month). It takes 38 months and costs $73 in interest to pay off, $373 total for $300 borrowed. Jordan borrows $300 from a credit union personal loan at 9% APR over 12 months. Monthly payment: $26. Total paid: $312. Same $300 borrowed. Different lenders, different rates. Alex paid $73 in interest. Jordan paid $12. The lender choice matters as much as the borrowing decision.
You need $400 for a car repair you can't cover from savings. Three options: credit card at 22% APR, personal loan from a credit union at 10% APR, or ask a parent for an interest-free loan.
Which is the most financially sensible choice?
Practice the idea
The framework for any borrowing decision: identify the APR, calculate the total repayment cost (there are free loan calculators online), and compare that cost to the value of what you're getting. If you're borrowing for something worth less than what you'll repay, reconsider.
Which choice best shows understanding of what debt is?
A student faces choosing between borrowing types for a needed repair. What is the smartest first step?
You borrow $500 at 18% APR and take 12 months to repay it. Roughly how much do you pay back in total?
What is the difference between useful debt and costly debt?
Bring it into your life
If you have any existing debt, identify the APR for each. List them from highest to lowest rate. Focus any extra payments on the highest APR debt first, that's where interest is costing you the most. Before any future borrowing, run the calculation: principal + estimated interest = total repayment. Decide if what you get is worth the total cost.
Debt is borrowed money repaid with interest, the interest is the cost of borrowing. A $500 loan at 18% APR over 12 months costs roughly $550 total. Useful debt generates value greater than the interest cost (education that boosts earning, a car needed for work). Costly debt funds things that don't generate financial return, the interest is pure loss. Before borrowing, calculate total repayment and ask whether the value exceeds that number.