On-Demand Instance vCPUs limits

There is a limit on the number of running On-Demand Instances per AWS account per Region. On-Demand Instance limits are managed in terms of the number of vCPUs that your running On-Demand Instances are using, regardless of the instance type. Each limit specifies the vCPU limit for one or more instance families.

• To see the current vCPUs limits of your account from AWS EC2 console
  • Enter "vcpu" in the "Find limits" to shortlist the limits
• To find out the current running instances (of the same instance family of the EC2 type you want to check), go to EC2 console.
• Calculate how many vCPUs you nee
  • You can use the vCPU limits calculator to see what will be the numbers for adding instances of certain type.
• Request a limit increase
  • Even though EC2 automatically increases your On-Demand Instance limits based on your usage, you can request a limit increase if necessary. See Request a limit increase for details.

See also https://aws.amazon.com/premiumsupport/knowledge-center/ec2-on-demand-instance-vcpu-increase/.