How Credit Scores Work

Before 1989, getting a loan depended heavily on who you knew, whether your banker liked you, and whether your face fit. Then FICO (Fair Isaac Corporation) introduced the modern credit score, and suddenly a formula, not a person, determined who got credit and at what price. It was meant to be fairer and more objective. Whether it succeeded is still debated. But understanding the formula is the first step to working with it.

The short answer

Your credit score is a statistical prediction of how likely you are to repay debt. Lenders use it to decide whether to give you a loan and at what rate. The score is calculated from your credit history using a formula that weighs five factors, and the company behind the most widely used formula is FICO, not any government agency or bank.

The full picture

Who actually makes your credit score

Most people assume the government or their bank controls their credit score. Neither does.

Your credit data is collected by three private companies called credit bureaus: Equifax, Experian, and TransUnion. These companies gather data from banks, credit card companies, lenders, and courts. They each maintain a separate file on you, which means your information might differ slightly across all three.

The score calculated from that data is produced by a separate company. FICO (Fair Isaac Corporation) produces the most widely used scoring models. According to FICO, lenders use FICO scores for roughly 90% of U.S. lending decisions. There’s also VantageScore, a competing model created by Equifax, Experian, and TransUnion together, which is used more often in free score services and some fintech apps.

Both models use scores ranging from 300 to 850. Generally:

• 800+: Exceptional
• 740-799: Very Good
• 670-739: Good
• 580-669: Fair
• Below 580: Poor

You don’t have one credit score. You have many, potentially dozens, depending on which bureau’s data is being used and which FICO model version the lender pulls.

The five factors (and how much each matters)

FICO hasn’t published its exact formula, but it has publicly disclosed how it weights the five categories of information it uses.

Payment history (35%): The single biggest factor. Have you paid your bills on time? A single missed payment, especially one more than 30 days late, can drop your score by 50-100 points. The damage fades over time, but a missed payment stays on your report for seven years.

Credit utilization (30%): How much of your available credit are you using? If you have a $10,000 credit limit and carry a $3,000 balance, your utilization is 30%. Most experts recommend staying below 30%, and ideally below 10%, for the best scores. This factor responds quickly: pay down a balance and your score can jump within a month.

Length of credit history (15%): How long have your accounts been open? This includes the age of your oldest account, your newest account, and the average age of all accounts. This is why closing an old credit card can hurt your score, even if you don’t use it.

Credit mix (10%): Having different types of credit (credit cards, installment loans, mortgages) is slightly better than having only one type. This signals you can manage different kinds of debt responsibly.

New credit (10%): How recently have you applied for new credit? Applying for several credit cards in a short period looks risky to lenders and temporarily lowers your score.

Hard inquiries vs. soft inquiries

When a lender checks your credit, it’s either a hard inquiry or a soft inquiry. The difference matters.

A hard inquiry happens when you apply for credit: a credit card, a car loan, a mortgage. It shows up on your report and can lower your score by a few points, typically 5 or fewer. Multiple hard inquiries in a short period suggest you’re seeking a lot of credit, which is a mild red flag. Mortgage and auto loan inquiries within a 14-45 day window are usually counted as a single inquiry, since lenders recognize you’re rate-shopping.

A soft inquiry happens when you check your own credit, or when a company pre-screens you for a pre-approved offer, or when an employer runs a background check. Soft inquiries have zero effect on your score.

This distinction matters because many people avoid checking their own credit, worried it will hurt them. It won’t. Check as often as you want.

What actually moves your score

The fastest way to hurt your score: miss a payment. Even one payment more than 30 days late causes significant damage.

The fastest way to improve it: reduce credit card balances. Because utilization is 30% of your score and updates monthly, paying down debt can show a meaningful improvement within 30-60 days.

Other positive moves that take time:

• Never miss another payment (a perfect track record gradually outweighs old mistakes)
• Keep old accounts open (preserves your credit history length)
• Only apply for new credit when necessary (each application causes a small, temporary dip)

Rebuilding a damaged score is slow. There’s no shortcut. The negative marks fade, but it takes years.

Why this affects more than just loans

Your credit score influences your interest rate on mortgages, car loans, and personal loans. The difference between a 620 score and a 760 score on a $300,000 mortgage can be 1-2% in interest rate, which translates to roughly $50,000-$100,000 more in interest paid over 30 years.

But it goes further. Landlords check credit scores. Some employers run credit checks. Car insurance companies in most U.S. states use credit-based insurance scores to set premiums. Utility companies may require deposits from people with low scores.

A score you’ve never explicitly managed can quietly shape where you live, what you pay for insurance, and whether you get certain jobs.

The credit bureau data problem: errors are common

Here’s something that should unsettle you: a 2013 Federal Trade Commission (FTC) study found that roughly 26% of consumers — about 1 in 4 — had a material error on at least one of their three credit reports. Some of these errors are minor: a wrong address, an account listed twice. Others are severe: accounts that belong to someone with a similar name, debts that have already been paid but are still listed as outstanding, or derogatory marks that should have aged off the report but haven’t.

The process for disputing errors is slow and often frustrating. You’re legally entitled to dispute any inaccurate information, and the bureau must investigate within 30 days. But the investigation typically means they send a form to the original creditor (the bank, the collection agency), who confirms or denies the error. If the creditor says the information is correct (whether or not it is), the bureau usually keeps it.

The Consumer Financial Protection Bureau (CFPB) received approximately 2.7 million credit or consumer reporting complaints in 2024 alone (as of March 2026, per the CFPB’s 2024 Consumer Response Annual Report). A significant portion involve disputes where the consumer believes the bureau is reporting incorrect information but won’t correct it.

This is why checking all three of your credit reports — free at AnnualCreditReport.com, once per year from each of the three bureaus (Equifax, Experian, TransUnion) — is genuinely worthwhile. Not just to understand your score, but to catch errors before they cost you on a mortgage application.

Why it matters

Credit scores are an abstraction of trustworthiness, and they’re an imperfect one. They don’t measure income, job stability, savings, or whether you’re actually a financial risk. Someone who pays rent in cash their entire life builds no credit history and scores poorly, even if they’ve never defaulted on anything.

Still, the system is what it is. Understanding the five factors gives you actual control: pay on time, keep utilization low, don’t close old cards, don’t apply for new credit unless needed. These four habits will get most people to a good score over time.

Common misconceptions

“My income affects my score.” It doesn’t. Lenders consider your income separately when evaluating applications, but the score itself is based entirely on your credit history, not your earnings.

“Checking my own score hurts it.” Only hard inquiries (from lenders) affect your score. Checking your own credit is a soft inquiry and has no impact.

“Carrying a small balance helps your score.” This one persists, but it’s false. Paying your balance in full every month is better for your score than carrying a balance.