On-Demand Instances - Amazon Elastic Compute Cloud

On-Demand Instances

With On-Demand Instances, you pay for compute capacity by the second with no long-term commitments. You have full control over its lifecycle—you decide when to launch, stop, hibernate, start, reboot, or terminate it.

There is no long-term commitment required when you purchase On-Demand Instances. You pay only for the seconds that your On-Demand Instances are in the running state. The price per second for a running On-Demand Instance is fixed, and is listed on the Amazon EC2 Pricing, On-Demand Pricing page.

We recommend that you use On-Demand Instances for applications with short-term, irregular workloads that cannot be interrupted.

For significant savings over On-Demand Instances, use AWS Savings Plans, Spot Instances, or Reserved Instances.

Work with On-Demand Instances

You can work with On-Demand Instances in the following ways:

If you're new to Amazon EC2, see How to get started with Amazon EC2.

On-Demand Instance 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 virtual central processing units (vCPUs) that your running On-Demand Instances are using, regardless of the instance type.

There are six On-Demand Instance limits, listed in the following table. Each limit specifies the vCPU limit for one or more instance families. For information about the different instance families, generations, and sizes, see Amazon EC2 Instance Types.

On-Demand Instance limit name Default vCPU limit

Running On-Demand All Standard (A, C, D, H, I, M, R, T, Z) instances

1152 vCPUs

Running On-Demand All F instances

128 vCPUs

Running On-Demand All G instances

128 vCPUs

Running On-Demand All Inf instances

128 vCPUs

Running On-Demand All P instances

128 vCPUs

Running On-Demand All X instances

128 vCPUs


New AWS accounts might start with limits that are lower than the limits described here.

With vCPU limits, you can use your limit in terms of the number of vCPUs required to launch any combination of instance types that meet your changing application needs. For example, with a Standard instance limit of 256 vCPUs, you could launch 32 m5.2xlarge instances (32 x 8 vCPUs) or 16 c5.4xlarge instances (16 x 16 vCPUs), or a combination of any Standard instance types and sizes that total 256 vCPUs. For more information, see EC2 On-Demand Instance limits.

Calculate how many vCPUs you need

You can use the vCPU limits calculator to determine the number of vCPUs that you require for your application needs.

When using the calculator, keep the following in mind: The calculator assumes that you have reached your current limit. The value that you enter for Instance count is the number of instances that you need to launch in addition to what is permitted by your current limit. The calculator adds your current limit to the Instance count to arrive at a new limit.

The following screenshot shows the vCPU limits calculator.

                    The vCPU limit calculator in the Amazon EC2

You can view and use the following controls and information:

  • Instance type – The instance types that you add to the vCPU limits calculator.

  • Instance count – The number of instances that you require for the selected instance type.

  • vCPU count – The number of vCPUs that corresponds to the Instance count.

  • Current limit – Your current limit for the limit type to which the instance type belongs. The limit applies to all instance types of the same limit type. For example, in the preceding screenshot, the current limit for m5.2xlarge and c5.4xlarge is 1,920 vCPUs, which is the limit for all the instance types that belong to the All Standard instances limit.

  • New limit – The new limit, in number of vCPUs, which is calculated by adding vCPU count and Current limit.

  • X – Choose the X to remove the row.

  • Add instance type – Choose Add instance type to add another instance type to the calculator.

  • Limits calculation – Displays the current limit, vCPUs needed, and new limit for the limit types.

    • Instance limit name – The limit type for the instance types that you selected.

    • Current limit – The current limit for the limit type.

    • vCPUs needed – The number of vCPUs that corresponds to the number of instances that you specified in Instance count. For the All Standard instances limit type, the vCPUs needed is calculated by adding the values for vCPU count for all the instance types of this limit type.

    • New limit – The new limit is calculated by adding Current limit and vCPUs needed.

    • Options – Choose Request limit increase to request a limit increase for the corresponding limit type.

To calculate the number of required vCPUs

  1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

  2. From the navigation bar, select a Region.

  3. From the left navigator, choose Limits.

  4. Choose Calculate vCPU limit.

  5. Choose Add instance type, choose the required instance type, and specify the required number of instances. To add more instance types, choose Add instance type again.

  6. View Limits calculation for the required new limit.

  7. When you've finished using the calculator, choose Close.

Request a limit increase

You can request a limit increase for each On-Demand Instance limit type from the Limits page or the vCPU limits calculator in the Amazon EC2 console. Complete the required fields on the AWS Support Center limit increase form with your use case. For Primary Instance Type, select the limit type that corresponds to the Instance limit name in the vCPU limits calculator. For the new limit value, use the value that appears in the New limit column in the vCPU limits calculator. For more information about requesting a limit increase, see Amazon EC2 service quotas.

Monitor On-Demand Instance limits and usage

You can view and manage your On-Demand Instance limits using the following:

For more information, see Amazon EC2 service quotas in the Amazon EC2 User Guide for Linux Instances, Viewing a Service Quota in the Service Quotas User Guide, and AWS Trusted Advisor.

With Amazon CloudWatch metrics integration, you can monitor EC2 usage against limits. You can also configure alarms to warn about approaching limits. For more information, see Using Amazon CloudWatch Alarms in the Service Quotas User Guide.

Query the prices of AWS services

You can use the Price List Service API or the AWS Price List API to query the prices of On-Demand Instances. For more information, see Using the AWS Price List API in the AWS Billing and Cost Management User Guide.