The billing cycle begins the first of the month, regardless of when you sign up. Your first month will be prorated based on your actual signup date.
Datadog meters the count of hosts, containers and custom metrics hourly. The billable count of hosts and containers is calculated at the end of the month using the maximum count (high-water mark) of the lower 99 percent of usage for those hours. We exclude the top 1% to reduce the impact of spikes in usage on your bill. The billable count of custom metrics is based on the average number of custom metric hours for the month.
What counts as a host?
Hosts are defined as any instances with the Datadog agent installed plus any AWS EC2s, GCP, Azure or vSphere VMs monitored via our integrations. Any EC2s or VMs with the agent installed will count as a single instance and will not be double-billed.
Note on containers: It is generally recommended that containers are monitored via a single containerized agent per host. This agent will collect both container and host metrics. If you choose to install the agent directly in each container, each container will be counted as a host from a billing perspective. More details can be found in our agent installation docs.