How a credit score is calculated, without the pie-chart myths

Almost everyone makes this mistake once. You see FICO’s pie chart, read that payment history is 35% of your score, and figure a perfect payment record must be worth about 298 points (35% of 850 is 297.5). Then you notice you’ve never missed a payment and your score is 640, and the math stops making sense.

It stops making sense because the score isn’t built like that. There’s no bucket of 298 points waiting to be filled. Understanding what the model actually does explains why two people with “perfect payment history” can sit far apart on the scale, and it tells you where your own effort will count.

What the model is trying to predict

A credit score is a ranking. myFICO describes FICO Score 8 as designed “to predict the likelihood of not paying as agreed in the future on any credit obligation.” The model looks at your credit report, compares the patterns in it with the patterns of past borrowers whose outcomes are already known, and places you on the 300 to 850 scale. Higher means the people who looked like you on paper were less likely to fall behind.

Two consequences follow from that:

• The score only sees your credit report. myFICO says the score “is calculated only from the information in your credit report.” Your income, savings, rent payments (unless reported), job history and bank balance aren’t inputs. A lender may look at your income and employment when deciding on an application, but that’s the lender’s decision process, separate from the score.
• No point table exists. Because the score is a statistical ranking, the effect of any one item depends on everything else in your file. FICO says “it’s not possible to measure the exact impact of a single factor” without looking at the whole report.

The five categories and what feeds each one

FICO groups report data into five categories and publishes how important each is for the general population. The right-hand column shows which parts of your report feed each category.

FICO’s own wording on each category is more careful than the pie chart. On payment history: “This is the most important factor in a FICO Score.” On amounts owed: using a lot of your available credit “may indicate that you are overextended.” On length of history: longer is generally positive “but is not required for a good credit score.” On credit mix: “it’s not necessary to have one of each.”

The new credit category has one more detail. Hard inquiries stay on your report for up to two years, but myFICO says they only affect FICO Scores for one year, and checking your own credit never counts.

Why the percentages are not points

FICO says outright that “the importance of these categories may vary from one person to another” and that the weights shown are “for the general population.” The same item can matter more in one file than in another, because the model is weighing it against everything else you’ve got.

Take two people who each have a single 30-day late payment from four months ago.

• Person A has 15 years of history, five accounts, and no other negatives.
• Person B opened a first card 14 months ago and has no other accounts.

Both have “one late payment,” but the late payment is a much larger share of Person B’s entire record. A model comparing each person to people with similar files will treat that late payment differently. Nobody outside FICO can tell you the point difference, and FICO doesn’t publish it, but the direction is clear: the thinner the file, the more any single event weighs. Our page on how late payments affect scores covers what FICO has published about that.

Amounts owed: the category you can change this month

Most categories move slowly. Late payments stay for years, and age only grows one month at a time. Amounts owed is different, because it mainly reflects the balances your issuers reported most recently. Run the numbers on your own cards. In this example you have two:

Overall utilization is $3,000 ÷ $8,000 = 37.5%. Now say you have $2,200 to put toward the cards before their statements close. You pay Card 2’s full $1,500 and $700 on Card 1, which leaves Card 1 at $800 and Card 2 at $0. The new reported total is $800 ÷ $8,000 = 10%, and the highest single card drops from 50% to 16% ($800 ÷ $5,000).

FICO says lower utilization is better and sets no official target. What makes this category different is that once the lower balances are reported, the next score calculation reads them. The utilization planner does this arithmetic across all your cards, and credit utilization, explained covers timing.

The minimum file needed to get a score at all

Before any of the five categories come into play, your report has to qualify. myFICO lists three requirements for a FICO Score:

1. At least one account opened for six months or more.
2. At least one account reported to the bureau within the past six months.
3. No indication on the report that you’re deceased.

One account can satisfy both of the first two. If you’re new to credit and keep seeing “no score available,” the six-month clock on your first account is usually why. VantageScore uses different methods for thin files, including machine learning on files with sparse histories, according to the company, which is one reason the two can disagree. More on that in FICO vs. VantageScore.

Where to put your effort

Start with the categories that can hurt you fastest.

• Protect payment history first. It’s FICO’s most important category, and one new late payment can outweigh months of other progress. Set up at least a minimum-payment autopay on every account.
• Work the balance side before any application. It’s the category that responds to this month’s reported numbers.
• Don’t open accounts for the “mix.” FICO says you don’t need one of each type, and every new account adds an inquiry and lowers your average age.
• Read your reason codes. Every score you pull comes with the top factors holding it down. Credit score reason codes, decoded translates them into specific report items.
• Check the inputs. The score can only be as accurate as the report. Pull all three free at AnnualCreditReport.com and dispute anything inaccurate.