What is calculated as a user-based license for agents in Zendesk?

Light agents and contributor roles are excluded, and all agents with capacity, including administrators and account owners, occupy a user-based license for agents. 

Depending on the product, a Support user-based license may be required. For a complete list, refer to the Managing user-based licenses for Support agents document.

Suspended agents occupy a user-based license. To secure a user-based license, Zendesk recommends downgrading the agent's account before suspending it.

Light agents, who are also Chat and Guide agents, occupy a user-based license. For example, an account with the Zendesk Suite has 5 user-based licenses for agents. If the account consists of 1 administrator, 3 agents, and 10 light agents, it is considered to have 1 available user-based license for agents. However, if 1 of the 10 light agents is also a Chat agent, that agent occupies the last user-based license, meaning no additional agents can be added to this account.