Your FICO credit score is determined by five factors: payment history (35%), amounts owed / credit utilization (30%), length of credit history (15%), credit mix (10%), and new credit inquiries (10%). Payment history and utilization together account for 65% of your score.
myFICO — the consumer education arm of Fair Isaac Corporation, which developed the FICO score — defines the five factor weights used in the most widely deployed FICO scoring models:
Whether you pay your accounts on time is the single largest driver of your credit score. What's tracked: payment status on credit cards, mortgages, auto loans, student loans, and personal loans; public records (bankruptcies, liens); collections accounts. A 30-day late payment can drop a good-credit borrower (720+) by 60–110 points. Payments older than 7 years are removed from your report. Setting autopay for at least the minimum payment on every account is the most reliable protection.
How much of your available revolving credit you're using. Calculated two ways: per-card (each individual card's balance ÷ limit) and aggregate (all card balances ÷ all card limits). The threshold that damages scores most is above 30% on any card or overall; above 50% begins having a more severe impact. Below 10% aggregate utilization is associated with the highest FICO scores. This factor recalculates every billing cycle — it responds to changes faster than any other factor.
Three sub-signals: age of your oldest account, age of your newest account, and average age of all accounts. A longer credit history provides more data and is viewed as more predictive. Don't close old accounts unless the annual fee is unjustified — closing an old card shortens your average account age and removes available credit (raising utilization).
Having experience with both revolving credit (credit cards, lines of credit) and installment credit (mortgage, auto loan, student loan, personal loan) demonstrates broader credit management ability. You don't need to open new accounts just to improve credit mix — this factor is a secondary signal and doesn't justify taking on debt you don't need.
Two signals: how many new accounts you've opened recently, and how many hard inquiries (formal credit applications) are on your report. Each new hard inquiry can temporarily lower your score 5–10 points. FICO groups rate-shopping inquiries for the same loan type (mortgage, auto, student loan) within a 45-day window as a single inquiry — so shopping rates across multiple lenders in a short window doesn't multiply the damage.