What Is Debt?
Debt is borrowed money you're obligated to repay, typically with interest. It's one of the most powerful tools in personal finance — used well, it enables things that would otherwise take decades to accumulate (like a home or an education). Used poorly, it becomes a compounding drain that outlasts the thing it financed.
Understanding debt starts with understanding its mechanics: the principal (what you borrowed), the interest rate (the cost of borrowing), and the term (how long you have to repay).
How Interest Works
Interest is the price of borrowing. It's charged as a percentage of the outstanding balance, typically expressed as an annual percentage rate (APR).
There are two types:
- Simple interest is calculated only on the principal. A $1,000 loan at 10% simple interest charges $100 per year regardless of balance.
- Compound interest is calculated on both the principal and the accumulated interest. This is how most consumer debt works. A $1,000 credit card balance at 20% APR, left unpaid, doesn't just cost $200 per year — the interest itself accrues interest, and the balance grows faster than it might seem.
Compound interest works powerfully for you in investments. It works powerfully against you in debt.
The True Cost of Debt
The monthly payment on a loan is visible. The total cost is often not. A $20,000 car loan at 7% over 5 years has a monthly payment of about $396, but the total repaid is roughly $23,760 — nearly $4,000 more than you borrowed.
Understanding the total cost, not just the monthly payment, is essential to making good borrowing decisions. Extending a loan term to lower monthly payments typically increases the total cost significantly.
Debt's Effect on Cash Flow
Every debt payment is a fixed commitment on your monthly income. The more of your income is committed to debt payments, the less flexibility you have. Lenders use the debt-to-income ratio (total monthly debt payments ÷ gross monthly income) to assess creditworthiness. A ratio above 40% begins to indicate financial stress.
High debt loads reduce the amount you can save and invest, directly slowing wealth accumulation.