How Credit Scores Work: The Five Factors Behind the Three Digits
By the Stoia team · August 16, 2026 · 6 min read
A credit score is not a grade on your character or a measure of your wealth. It is a three-digit prediction, built from your credit report, of one narrow thing: how likely you are to fall seriously behind on a debt in the next couple of years. Everything strange about scores, why income does not count, why closing a card can hurt, why a paid-off millionaire can score lower than a careful student, follows from that one design goal.
The five factors and their weights
The dominant model, the FICO score, weighs five ingredients. The percentages are published by its maker and have been stable for years:
- Payment history: 35%. Did you pay on time, every time? A single payment reported 30 days late can outweigh years of good behavior, and the damage scales at 60 and 90 days. Nothing else comes close to this factor's power, in both directions.
- Amounts owed: 30%. Mostly your credit utilization, the share of your card limits currently in use. Someone using $450 of a $10,000 limit reads as in control; someone using $9,000 of it reads as strained, even if both pay on time. The credit utilization calculator shows where you stand overall and per card.
- Length of credit history: 15%. The age of your oldest account, the average age of all of them, and how long since each was used. Time is the one input you cannot rush.
- New credit: 10%. Recent applications, each one a hard inquiry, plus how many accounts are newly opened. A burst of applications reads as distress.
- Credit mix: 10%. Experience across revolving accounts (cards) and installment loans (auto, student, mortgage). A minor factor; never take on a loan just to diversify it.
The bands lenders actually use
| FICO range | Band | What it typically means |
|---|---|---|
| 800–850 | Exceptional | Best pricing on nearly everything |
| 740–799 | Very good | Top-tier rates on most products |
| 670–739 | Good | Approved widely, decent but not best rates |
| 580–669 | Fair | Approvals get selective, pricing worsens fast |
| 300–579 | Poor | Mostly secured products and deposits required |
Two truths about the bands. First, thresholds beat points: moving from 738 to 742 can change a mortgage quote, while 30 points inside the same band may change nothing. Second, above roughly 780 the game is over; chasing 850 buys you nothing a 790 does not.
Myths that cost real points
"Checking my score hurts it." False. Checking your own score or report is a soft inquiry and never affects anything. Only applications for new credit generate hard inquiries, and even those typically cost only a few points for under a year.
"Carrying a balance builds credit." The most expensive myth in America. Scores see the balance your card issuer reports each month, not whether you paid interest on it. Pay in full every month and your score benefits identically while your interest cost stays at zero. Nobody at any scoring company has ever rewarded interest paid.
"Income and assets matter." Neither appears anywhere in the calculation. Lenders consider income separately when they underwrite; the score itself only reads borrowing behavior.
"Closing paid-off cards is tidy." Closing a card removes its limit from your utilization math and, years later, its age from your file. Keeping a no-fee card open with a small recurring charge is usually the better move.
The fastest levers, in order
- Never miss a due date again. Autopay the minimum on everything as a floor, even if you pay in full manually.
- Push utilization down before the statement closes. Utilization has no memory: it is recalculated from each new statement, so paying a card down before the reporting date can move a score within a cycle or two.
- Dispute actual errors. A wrongly reported late payment or a stranger's account is worth formal dispute with each bureau; fixing one can outdo years of optimization.
- Then stop optimizing. Beyond on-time payments, low utilization, and patience, the remaining levers are small. If you are starting with no file at all, the playbook is different: see how to build credit from scratch.
A score is one lens on your finances, and a deliberately narrow one: it cannot see your savings, your investments, or whether the debt it prices ever bought you anything. Stoia is being built to show the whole picture those three digits leave out, every account and obligation in one place, so the score becomes one gauge on the dashboard instead of the dashboard itself.