Credit utilization is FICO's second-biggest factor — 30% of your score, second only to payment history. The math is simple: reported balance divided by total credit limit. The trap is the denominator. When an unused card gets closed by the bank for inactivity, that limit vanishes overnight, and your utilization spikes without you spending a dollar.
Utilization = total reported balance ÷ total credit limit. Aim for under 10%. The most common silent score drop: an unused card the bank closes for inactivity. Your denominator shrinks, utilization climbs, score falls — without any change to your spending.
Protect the denominator → or jump to pricingThe math
Total reported balance across all revolving accounts ÷ total credit limit. Reported balance is what bureaus see — typically your statement balance at close. Total limit is the sum across every open credit card.
Example: three cards with limits of $10,000, $5,000, and $3,000 ($18,000 total). Reported balances $1,500, $0, and $200 ($1,700 total). Utilization: $1,700 / $18,000 = 9.4%.
FICO computes this two ways — per-account and aggregate. Both matter. The aggregate is what most score apps display and what lenders weight heaviest.
The target
- Below 30% — the broadly cited "good" zone.
- Below 10% — where serious optimization lives.
- 1–3% — optimal. Low but not zero.
0% across every card slightly hurts in some FICO versions — it reads as "no recent activity." Keep one card with $5–$50 reported each cycle; the rest can be $0.
Per-account utilization matters too. Even at 5% aggregate, a single card at 80% utilization signals risk. Spread balances, or pay down concentrated cards before statement close.
What "reported balance" is
Bureaus see your balance on a specific date each month — usually statement close. Your peak spending during the cycle is invisible. Paying down before statement close reduces the snapshot. You can spend $5,000 in a month, pay $4,500 before close, and report $500.
The dormant-card trap
The mechanic that catches almost everyone. Closing a card removes its limit from your denominator immediately. Your utilization ratio rises even though nothing about your spending changed.
Same three-card portfolio. The bank closes the $5,000 card for inactivity. New available credit: $13,000. Same $1,700 in balances. New utilization: 13.1%. The score drops without you doing anything.
This is why letting unused cards go dormant has a real cost. A sock-drawer card silently contributing $5,000 to your denominator is doing useful score work — until the bank closes it. The defense is small: a $1 monthly charge keeps the card open and the denominator intact.
Common mistakes
Closing unused cards "to simplify." Direct utilization hit. Closure only makes sense for annual fees you can't downgrade or security issues. "I don't use it" isn't a reason.
Paying after statement close. The snapshot is already taken. Pay before close to control the reported number.
Concentrating spend on one card. Even with low aggregate, one card at 80% looks like high risk. Spread, or mid-cycle pay-down.
Action items
- Don't close unused cards. They're free denominator.
- Pay down before statement close, not after.
- Keep one card with a small reported balance.
- Protect every unused card from inactivity closure.
Why dormancy is the dormant lever
Most utilization advice is about the numerator — pay it down, time the cycle, request a CLI. All correct. The cheapest move most people miss is on the denominator side: an unused credit line is contributing limit until something takes it away. Your decision to close costs you. The bank's decision to close for inactivity costs you the same way, and you don't see it coming.
Set up a small activity layer on each card you're not actively using. The maintenance cost is tiny; the score protection is real, immediate, and durable.