How Your Credit Score Is Actually Calculated
Your FICO credit score is a three-digit number between 300 and 850 that lenders use to predict how likely you are to repay borrowed money. It is built from five components, each with a fixed weight, published openly by FICO. Most of the personal-finance internet misses one of those weights, usually because they're guessing, not reading the source.
Payment history (35%)
More than a third of your score comes from one question: do you pay on time? A single 30-day late payment can knock 60–110 points off a high score and stays on your report for seven years. Set every minimum payment on autopay the day the account opens. You can pay extra manually, but never miss the minimum.
Credit utilization (30%)
Utilization is the percentage of your available revolving credit you're currently using. If you have $10,000 in card limits and a $3,000 balance, your utilization is 30%. Below 30% is fine, below 10% is ideal, and 0% is very slightly worse than 1–9% (the algorithm wants to see you using credit, just responsibly). This is the one factor you can change in 30 days, pay down balances before the statement closes, not before the due date.
Length of credit history (15%)
The average age of your accounts matters, and it can only go up with patience. The most common self-inflicted mistake is closing your oldest credit card because you don't use it, that drops your average age and shrinks your total available credit (raising utilization). Keep old no-fee cards open and put a small recurring subscription on them.
Credit mix (10%) and new credit (10%)
Lenders like to see that you can responsibly handle different types of credit, revolving (cards) and installment (auto loans, mortgages, student loans). You don't need to take out a loan for the sake of mix, but if you have one it helps. New credit is the flip side: opening multiple accounts in a short window tells the algorithm you're stretching, and each hard inquiry dings your score by a few points for about a year.