Here's everything I know about the credit score system explained in terms of what actually matters for your number.

Payment history (35%): the single most impactful factor. One 30-day late payment can drop a score by 50-100 points. Fix: autopay on everything, minimum payment at minimum.

Credit utilization (30%): ratio of credit used to credit available across all revolving accounts. Under 10% is excellent. Under 30% is acceptable. Over 50% is damaging. Fix: pay down balances and/or request credit limit increases without increasing spending.

Length of credit history (15%): average age of accounts, age of oldest account. Fix: don't close old cards, even if you don't use them. Put a small recurring charge on old cards to keep them active.

Credit mix (10%): having both revolving (credit cards) and installment (loans) credit. Fix: usually not worth manufacturing — the natural mix from real use develops over time.

New credit (10%): hard inquiries from new applications. Each inquiry drops your score 2-5 points temporarily. Fix: don't apply for new credit unnecessarily.

The three most impactful behaviors: pay on time always, keep utilization low, don't close old accounts.