30% utilization spread across four cards is meaningfully better for your credit score than 90% on one card. FICO weighs both your overall utilization (sum of balances divided by sum of credit limits) and the highest single-card utilization. The single-card metric is the second factor that catches many people; even with low overall utilization, a single maxed-out card can drag your score down by 30-60 points.
How utilization is calculated. Overall utilization = total balances / total credit limits. If you have $3,000 in total balances across $10,000 in credit limits, your overall utilization is 30%. Single-card utilization is the same calculation per card. FICO looks at both metrics; the score is suppressed if either is high.
Concrete comparison. Scenario A: $750 balance on each of 4 cards with $2,500 limits each. Total: $3,000 balance / $10,000 credit. Overall utilization: 30%. Highest single card: 30%. Both metrics moderate. Scenario B: $9,000 balance on one card with $10,000 limit. Total: $9,000 balance / $10,000 credit. Overall utilization: 90%. Highest single card: 90%. Both metrics extreme.
Score impact. Scenario A typically suppresses your score by 5-15 points compared to all balances under 10% utilization. Scenario B typically suppresses your score by 60-100+ points. The same total dollar amount of debt produces dramatically different scores depending on how it is distributed.
Why FICO weights single-card utilization. A single maxed card is statistically associated with financial distress in the FICO model, even if overall utilization is moderate. The model treats high single-card utilization as a signal that the cardholder is approaching their credit limit and may default. Spreading the same balance across multiple cards is less statistically associated with distress.
Implication for payoff strategy. When paying down credit cards, consider not just APR (avalanche method) or balance (snowball method) but also single-card utilization. Bringing one maxed card from 95% to 70% may yield a bigger score boost than bringing two moderate-utilization cards from 30% to 20%. This is especially relevant if you are about to apply for a mortgage or auto loan.
The 30% myth. Many sources claim 30% utilization is a magic threshold for good credit. The actual FICO model is continuous; lower is always better. A score under 10% utilization is materially better than 30%. The 30% number became conventional wisdom because it is roughly the boundary where score impact starts to become noticeable, not because anything special happens at that point.
How to manage utilization for a specific event. If you have a mortgage application or refinance pending, pay down balances 7-10 days before each card's statement closing date (the date the bureaus get reported). This way the bureaus see lower balances. The same payment after statement close will not be reflected for another 30 days.