A credit score gets treated like a single, opaque number, but it’s actually a weighted sum of five specific, individually knowable factors — and the weighting itself is public information, published directly by FICO, not a secret formula. Knowing the actual percentages changes which financial habit is worth prioritizing first, because they are genuinely not equal.

Payment history — 35%, and by far the largest single factor

Whether you’ve paid your bills on time is the single heaviest input into a FICO score, accounting for 35% of the total calculation — more than any other factor by a wide margin. This covers credit cards, loans, and any other credit account, and the scoring model weighs recency and severity: a missed payment from six years ago carries far less weight than one from six months ago, and a single 30-days-late mark carries less damage than an account that went to collections. The outsized weight here reflects what payment history actually predicts — it’s the most direct evidence of whether someone reliably pays back what they owe, which is the core question a credit score exists to answer.

Amounts owed / credit utilization — 30%

The second-largest factor, at 30%, is how much of your available credit you’re actually using — your utilization ratio. This isn’t simply “how much debt you carry” in absolute dollars; it’s a ratio, comparing your current balances against your total available credit limits. A high utilization ratio, even if every payment has been made on time, signals higher risk to the scoring model, which is why paying down a high balance can move a score noticeably even without any change to payment history at all.

Length of credit history — 15%

How long your credit accounts have existed makes up 15% of the score, factoring in the age of your oldest account, your newest account, and the average age across all of them. This factor is structurally difficult to improve quickly — there’s no faster way to increase it than time itself passing, which is part of why closing an old, unused credit card can quietly hurt a score more than people expect: it can shorten your average account age even if it doesn’t add any new debt.

Credit mix — 10%

Ten percent of the score reflects the variety of credit types on your file — a combination of revolving credit (credit cards) and installment credit (auto loans, mortgages, personal loans) is viewed more favorably than having only one type, on the theory that successfully managing different kinds of credit obligations is itself evidence of financial reliability.

New credit inquiries — 10%

The remaining 10% covers recent applications for new credit. Each hard inquiry — a lender checking your credit specifically because you applied for something — can cause a small, typically temporary dip, on the logic that opening several new credit lines in a short window statistically correlates with higher near-term risk.

The actual takeaway

These five weightings — 35/30/15/10/10 — are FICO’s own published population-level averages, not a fixed rule that applies identically to every individual file; the actual impact of any one factor shifts depending on where a specific credit file is already strong or weak. But the ranking itself is genuinely useful to know: payment history and utilization together account for nearly two-thirds of the entire score, which means the two highest-leverage habits — paying on time and keeping balances low relative to limits — are also, not coincidentally, the two the scoring model weighs the most heavily.