The credit utilization formula is: Total Balances ÷ Total Credit Limits = Utilization Ratio.
Add all revolving balances and divide by all revolving limits combined. This is the primary method used by FICO 8 and VantageScore 4.0.
FICO also scores individual card utilization. A single maxed-out card hurts even if your aggregate is low.
FICO 10T tracks your utilization over 24 months. Consistently declining utilization is rewarded with higher scores than a single low snapshot.