How Credit Scores Work

What a Credit Score Is

A credit score is a three-digit number (typically 300–850) that summarizes your financial trustworthiness based on your borrowing and repayment history. It answers a single question lenders care about: "If I lend this person money, what's the probability they'll pay me back?"

The higher the score, the lower the risk. The lower the score, the higher the risk. Lenders price that risk into interest rates: low-risk borrowers get lower rates, high-risk borrowers get higher rates.

The most widely used model is FICO, developed by Fair Isaac Corporation and used by 90% of lenders. Other models exist (VantageScore, Experian, Equifax, TransUnion) but FICO dominates.

Why this matters: A borrower with a 780 FICO score might qualify for a 30-year mortgage at 6.5%. The same borrower with a 620 FICO score might qualify at 8.5%. On a $400,000 loan, that 2% difference is $400+/month or $144,000 over the 30-year life of the loan.

Your credit score directly translates to money: lower score = higher costs = less wealth.

How FICO Scores Are Calculated

FICO considers five factors. They don't weight equally:

1. Payment history (35% of score)

Do you pay bills on time? This is the most important factor.

• On-time payments: +points
• Late payments (30, 60, 90+ days): -points (more recent lates hurt more)
• Charge-offs, collections, bankruptcies: huge -points

A single late payment can drop your score 50–100 points. Multiple lates can drop it 100–200 points. The older the late payment, the less it hurts.

Bottom line: pay every bill on time, every month. This alone can get you from 650 to 750+.

2. Credit utilization (30% of score)

How much of your available credit are you using? If you have $10,000 in credit limits and carry a $3,000 balance, your utilization is 30%.

• 0–10% utilization: optimal (minimal points lost)
• 10–30% utilization: good (slight points lost)
• 30–50% utilization: fair (more points lost)
• 50%+ utilization: poor (significant points lost)
• 100% utilization: very poor (max points lost)

Utilization is calculated monthly based on your statement balance, not your payment history. Paying off a $3,000 balance to $900 (9% utilization) can raise your score 20–40 points immediately.

This is why carrying high credit card balances (even if you pay them off monthly) hurts your score: the high balance on your statement date is what gets reported.

3. Length of credit history (15% of score)

How long have you been borrowing?

• Average age of accounts: older is better
• Age of oldest account: matters more than average
• Recent accounts: slightly lower weight

Opening new credit cards lowers your average account age (slightly negative). But closing old accounts also lowers it (more negative). So keep old accounts open even after paying them off.

Someone with accounts 20 years old gets more points than someone with accounts 2 years old, all else equal.

4. Credit mix (10% of score)

Do you have different types of credit?

• Credit cards (revolving credit)
• Auto loans (installment credit)
• Mortgages (installment credit)
• Student loans (installment credit)

Lenders want to see you can handle different types of debt. Someone with only credit cards is slightly riskier than someone with credit cards + a mortgage. But credit mix is only 10%, so don't take out loans just for this.

5. New credit (10% of score)

How many new accounts have you recently opened?

• Hard inquiries: when you apply for credit, a lender checks your report. Each inquiry drops your score 5–10 points.
• Multiple hard inquiries in a short time: shows desperation, hurts more
• New accounts: lower points initially (young accounts have no history)

Applying for 3 credit cards in one month can drop your score 50–80 points. The impact fades over months as the new accounts age.

FICO Score Ranges

• 300–579: Poor. Difficulty getting approved; subprime rates (12–25%+ APR on credit).
• 580–669: Fair. Approval possible but with higher rates (10–15% APR on credit); mortgages at 7–8%.
• 670–739: Good. Standard approval, reasonable rates; mortgages at 6–7%.
• 740–799: Very good. Easy approval, better rates; mortgages at 5–6%.
• 800+: Exceptional. Best rates available; mortgages at sub-5%.

The jump from 620 to 680 is more valuable than the jump from 780 to 800. The first jump might save $2,000/year in interest; the second might save $200/year.

Why Your Score Matters Beyond Borrowing

Mortgages: A 100-point difference in credit score can mean a 1–2% difference in rates, costing $200–$400/month on a $400,000 mortgage.

Auto insurance: Some insurers use credit scores to price premiums. A low score might cost $50–$150/year more on auto insurance.

Credit card approvals: Low scores get denied or approved with high APRs (20–25%+). High scores get better terms (0% intro offers, higher limits, rewards cards).

Job offers: Some employers (especially financial services, government) check credit as part of background checks. Very bad scores (bankruptcy, collections) might impact hiring decisions.

Rental approvals: Landlords check credit scores. Low scores might result in higher deposits or outright rejection.

Utility deposits: Some utilities require security deposits for customers with poor credit.

How to Improve Your Score

Immediate (1–3 months):

• Pay down credit card balances to below 30% utilization. If you have $10,000 total credit limit and $8,000 balance, pay it down to $3,000. Score impact: +20–50 points.
• Make all payments on time. Even one new on-time payment starts rebuilding trust. Impact: gradual (+5–10 points/month initially, more as history builds).
• Dispute errors on your credit report. Errors happen: accounts that aren't yours, incorrect late payments, inaccurate balances. Check your reports at AnnualCreditReport.com (free, once yearly). Impact: +50–100+ points if errors exist.

Medium-term (6–12 months):

• Keep making all payments on time. Payment history is 35% of your score. Consistent on-time payments are the strongest signal. Impact: +50–200 points over time.
• Keep credit card balances low. Maintain utilization below 10% if possible. Impact: +10–20 points/month as balances drop.
• Don't apply for new credit. Avoid new hard inquiries. Impact: prevents 5–10 point drops.

Long-term (1–2 years):

• Keep old accounts open. Even after paying off credit cards, keep them open with small purchases (paid off monthly). Impact: maintains length of history, prevents score drops.
• Build diverse credit. If you only have credit cards, consider becoming an authorized user on someone's mortgage or adding an installment loan (auto loan, personal loan). Impact: +20–30 points for credit mix.
• Avoid new late payments. Continue perfect payment history. Impact: +5–10 points/month as older lates fall off report (after 7 years, they stop affecting your score).

A Worked Example

Starting score: 600 (due to past late payments and high credit utilization)

Month 1–3:

• Pay down credit card balance from 70% to 20% utilization: +40 points
• Make all payments on time: +10 points
• Dispute an inaccurate late payment on report: +30 points
• New score: 680

Month 4–12:

• Maintain on-time payments: +60 points
• Keep utilization at 20%: maintained
• Avoid new credit inquiries: prevent 30 point drop
• New score: 740

Year 2:

• Continue perfect payment history: +20 points
• Keep accounts open: maintained
• New score: 760

In 2 years, you've gone from 600 (subprime rates, difficulty borrowing) to 760 (very good rates, easy approval). The work: paying on time and keeping balances low. That's it.

Start This Week

1. Check your credit report free at AnnualCreditReport.com.
2. Identify errors and dispute them.
3. Check your credit card balances and utilization.
4. If utilization is above 30%, make a payment to reduce it.
5. Set up autopay for all bills to ensure on-time payments.
6. Check your score monthly at Credit Karma or Experian (free).

Your credit score is trackable and improvable. The actions are simple. The payoff is huge.