A credit score is a three-digit number (usually 300–850) that tells lenders how likely you are to pay back money you borrow. It shapes whether you get approved for loans and credit cards — and how much interest you'll pay — so understanding it is one of the most practical parts of personal finance.
What a Credit Score Actually Measures
A credit score is a summary of your credit history — your track record of borrowing and repaying. The most common model, FICO, runs from 300 to 850, and higher is better. Lenders use it to estimate risk: a high score signals you reliably pay on time, while a low score signals you might not.
You don't have just one score. Different lenders and models can produce slightly different numbers, but they all weigh similar information from your credit reports.
The Five Factors That Determine Your Score
Your score is built from five categories, each weighted differently: payment history (about 35%) — whether you pay on time, the single biggest factor; amounts owed (about 30%) — especially your credit utilization, or how much of your available credit you're using; length of credit history (about 15%) — how long you've had accounts; credit mix (about 10%) — the variety of credit types; and new credit (about 10%) — how many new accounts or applications you've had recently.
The two biggest levers are clear: pay every bill on time, and keep your balances low relative to your limits (a utilization under about 30% is a common guideline).
Why Your Credit Score Matters
A good score saves you real money. On a car loan or mortgage, a higher score can mean a much lower interest rate — potentially thousands of dollars over the life of the loan. Beyond loans, landlords often check credit before renting an apartment, utility and phone companies may check it, and some employers review a version of it for certain jobs.
In short, credit affects far more than borrowing — it's a reputation number that follows you into many adult financial decisions.
How to Build and Keep a Good Score
Pay on time, every time — set up automatic minimum payments so you never miss one. Keep your credit-card balances low. Don't close your oldest card (length of history helps you). Apply for new credit only when you need it. And check your credit reports for errors, which you can do for free.
Building credit takes time; there's no instant fix. Consistent, responsible habits are what move the number up.
Key Takeaways
- A credit score (300–850) predicts how likely you are to repay borrowed money.
- Payment history (~35%) and amounts owed (~30%) matter most.
- A higher score means lower interest rates and easier approval for loans, apartments, and more.
- Pay on time and keep credit utilization low to build a strong score.
Check Your Understanding: How Credit Scores Work
Five practice questions on How Credit Scores Work. Tap an answer to see whether you're right and why each choice is right or wrong.
1. Several things happened to Dev's credit this year. Which one falls under the “new credit” factor of his credit score?
Answer: A. New credit (about 10% of the score) looks at how many new accounts or applications you've had recently. Several applications in a short time can lower a score.
Why the other choices are wrong:
- B. A late payment falls under payment history, about 35% of the score.
- C. A high balance compared with the limit falls under amounts owed (credit utilization), about 30% of the score.
- D. The age of accounts falls under length of credit history, about 15% of the score.
2. Felipe has two credit cards. Card A has a $2,000 limit and a $900 balance. Card B has a $3,000 limit and a $600 balance. What is his overall credit utilization?
Answer: B. Total balances ÷ total limits = ($900 + $600) ÷ ($2,000 + $3,000) = $1,500 ÷ $5,000 = 30%.
Why the other choices are wrong:
- A. 20% is Card B's utilization alone ($600 ÷ $3,000). Overall utilization uses the balances and limits of both cards.
- C. This averages the two cards' rates (45% and 20%). Because the limits are different, you have to divide total balances by total limits instead.
- D. 45% is Card A's utilization alone ($900 ÷ $2,000). Overall utilization combines both cards.
3. Brianna, 20, says her credit score doesn't matter because she plans never to take out a loan. Which situation best shows why her score could still matter?
Answer: D. Landlords often check credit before renting an apartment, and utility and phone companies may check it too, so her score matters even if she never borrows.
Why the other choices are wrong:
- A. Debit card purchases use her own money and aren't reported to the credit bureaus, so they don't build or hurt her score.
- B. Income tax depends on income, not credit. Credit scores aren't used to figure out taxes.
- C. Credit scores affect the rates you pay to borrow, not the rates a bank pays you on savings.
4. Hana has two credit cards. Her oldest card has a $3,000 limit and a $0 balance. Her newer card has a $2,000 limit and an $800 balance. If she closes her oldest card, what will her credit utilization be?
Answer: C. With the oldest card closed, her only available credit is $2,000, so utilization = $800 ÷ $2,000 = 40%, up from 16%. Closing her oldest card could also eventually shorten her credit history.
Why the other choices are wrong:
- A. 16% is her utilization now ($800 ÷ $5,000). Closing the card removes its $3,000 limit, so the same balance is divided by less available credit.
- B. This divides her $800 balance by the closed card's $3,000 limit. After closing it, only the newer card's $2,000 limit is left.
- D. 60% is the share of the newer card's limit she is not using (($2,000 − $800) ÷ $2,000). Utilization measures the share she is using.
5. While checking her free credit report, Wren finds a credit card account she never opened, with a missed payment on it. What should she do?
Answer: A. An account she never opened is an error, and possibly a sign of identity theft. Disputing it with the credit bureau can get it removed, which protects her payment history.
Why the other choices are wrong:
- B. Paying a debt that isn't hers doesn't fix the error, and paying a past-due balance doesn't erase a late payment that was already reported. The account should be disputed.
- C. A new application counts against the new-credit factor and does nothing to remove the false missed payment. The error itself needs to be disputed.
- D. There's no instant fix for a credit score. Errors can be disputed for free, and building credit takes consistent habits over time.
Keep Studying
Related: Compound Interest, Gross vs. Net Pay.
These guides are educational and written for the AP Business with Personal Finance course. They provide general information, not personalized financial advice.