Credit scores can feel like a mysterious number that decides whether a lender says yes or no, but the underlying math is publicly documented and follows the same general logic across the two dominant scoring systems used in the United States: FICO and VantageScore. Understanding the ingredients that go into a score can make it easier to see why a score moves up or down over time and why two lenders might see slightly different numbers for the same person.
The Two Main Scoring Models
Most lenders in the US rely on FICO Scores, developed by the Fair Isaac Corporation, though VantageScore (created jointly by the three major credit bureaus) has become increasingly common, especially for free score-monitoring tools. Both models generally produce scores on a 300–850 scale, and both pull from the same underlying data: your credit reports held by Equifax, Experian, and TransUnion. Because each bureau may have slightly different information on file (not every creditor reports to all three), your FICO or VantageScore can vary somewhat depending on which bureau's data was used.
There are also multiple versions of each model (for example, older and newer FICO versions, and different generations of VantageScore), and different industries sometimes use industry-specific versions tailored to auto lending or credit cards. This is one reason the score you see from a free app may differ from the score a mortgage lender pulls.
The Core Factors FICO Considers
FICO has generally described its formula as weighing five broad categories, though the exact algorithm is proprietary:
- Payment history (roughly the largest single factor): Whether you have paid credit accounts on time. Late payments, collections, and derogatory marks like bankruptcy tend to have an outsized negative effect, and their impact generally fades somewhat as they age.
- Amounts owed / credit utilization: How much of your available revolving credit (mainly credit cards) you are using. Carrying balances close to your credit limits is typically viewed less favorably than keeping utilization low, even if you pay in full each month.
- Length of credit history: How long your accounts have been open, including the age of your oldest account and the average age of all accounts.
- Credit mix: Whether you have experience managing different types of credit, such as revolving accounts (credit cards) and installment loans (auto loans, personal loans, mortgages).
- New credit: How many accounts you have opened recently and how many hard inquiries appear on your report.
VantageScore uses a broadly similar set of inputs but sometimes weights them differently and can score people with thinner credit files that FICO's older models might not score at all.
Why the Same Data Can Produce Different Scores
Because there are multiple scoring models, multiple versions of each model, and three separate bureaus with potentially different data, it's normal to see a range of scores rather than one single number. Lenders often disclose which score version and bureau they use, and for major financing decisions like mortgages, it's common for lenders to pull scores from all three bureaus and use the middle value.
What Isn't Included
Certain information is generally excluded from credit score calculations, including income, employment status, age, race, marital status, and where you live. However, lenders may still separately consider factors like income and employment when deciding whether to approve a loan and at what terms — a credit score is only one part of a broader underwriting decision. For more on how a full application is evaluated, see how debt-to-income ratio factors into approval, and what documents lenders typically request.
Keeping Track of the Underlying Data
Because your score is a reflection of the data in your credit reports, it's worth periodically reviewing those reports for accuracy through free channels like AnnualCreditReport.com. If you find something inaccurate, there is a formal process for disputing credit report errors with the bureaus.
Putting the Ranges in Context
Once you understand what feeds into a score, it helps to know what the resulting number typically means for loan pricing and approval odds — see our breakdown of credit score ranges explained. Scores also react differently to different kinds of activity; for example, a single hard inquiry from a loan application has a different effect than a missed payment — a topic covered in how hard inquiries affect your credit score.
A Note on Precision
Because credit scoring formulas are proprietary and periodically updated, and because the weight of each factor can vary based on your overall credit profile, it is generally more useful to think of these categories as directional influences rather than a fixed formula you can calculate exactly at home. A credit counselor or financial advisor can help interpret your specific credit report factors and how they may be affecting your particular score.