# Statistics for CloudWatch metrics for your instances
You can get statistics for the CloudWatch metrics for your instances. *Statistics* are metric data aggregations over specified periods of time. CloudWatch provides statistics based on the metric data points provided by your custom data or provided by other services in AWS to CloudWatch. Aggregations are made using the namespace, metric name, dimensions, and the data point unit of measure, within the time period you specify. The following table describes the available statistics.
| Statistic | Description |
| --- | --- |
| Minimum | The lowest value observed during the specified period. You can use this value to determine low volumes of activity for your application. |
| Maximum | The highest value observed during the specified period. You can use this value to determine high volumes of activity for your application. |
| Sum | All values submitted for the matching metric added together. This statistic can be useful for determining the total volume of a metric. |
| Average | The value of `Sum` / `SampleCount` during the specified period. By comparing this statistic with the `Minimum` and `Maximum`, you can determine the full scope of a metric and how close the average use is to the `Minimum` and `Maximum`. This comparison helps you to know when to increase or decrease your resources as needed. |
| SampleCount | The count (number) of data points used for the statistical calculation. |
| pNN.NN | The value of the specified percentile. You can specify any percentile, using up to two decimal places (for example, p95.45). |
**Topics**
+ [
# Get statistics for a specific instance
](US_SingleMetricPerInstance.md)
+ [
# Aggregate statistics across instances
](GetSingleMetricAllDimensions.md)
+ [
# Aggregate statistics by Auto Scaling group
](GetMetricAutoScalingGroup.md)
+ [
# Aggregate statistics by AMI
](US_SingleMetricPerAMI.md)
# Get statistics for a specific instance
You can use the AWS Management Console or the AWS CLI to get statistics for a specific instance. The following examples show you how to use the AWS Management Console or the AWS CLI to determine the maximum CPU utilization of a specific EC2 instance.
**Requirements**
+ You must have the ID of the instance. You can get the instance ID using the AWS Management Console or the [describe-instances](https://docs.aws.amazon.com/cli/latest/reference/ec2/describe-instances.html) command.
+ By default, basic monitoring is enabled, but you can enable detailed monitoring. For more information, see [Manage detailed monitoring for your EC2 instances](manage-detailed-monitoring.md).
**To display the CPU utilization for a specific instance (console)**
1. Open the CloudWatch console at [https://console.aws.amazon.com/cloudwatch/](https://console.aws.amazon.com/cloudwatch/).
1. In the navigation pane, choose **Metrics**.
1. Choose the **EC2** metric namespace.
1. Choose the **Per-Instance Metrics** dimension.
1. In the search field, enter **CPUUtilization** and press Enter. Choose the row for the specific instance, which displays a graph for the **CPUUtilization** metric for the instance. To name the graph, choose the pencil icon. To change the time range, select one of the predefined values or choose **custom**.
![\[Graph a single metric\]](http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/images/metric_statistics_ec2_instance.png)
1. To change the statistic or the period for the metric, choose the **Graphed metrics** tab. Choose the column heading or an individual value, and then choose a different value.
![\[Change the statistic or period for a metric\]](http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/images/metric_statistics_ec2_instance_statistic_period.png)
**To get the CPU utilization for a specific instance (AWS CLI)**
Use the following [get-metric-statistics](https://docs.aws.amazon.com/cli/latest/reference/cloudwatch/get-metric-statistics.html) command to get the **CPUUtilization** metric for the specified instance, using the specified period and time interval:
```
aws cloudwatch get-metric-statistics --namespace AWS/EC2 --metric-name CPUUtilization --period 3600 \
--statistics Maximum --dimensions Name=InstanceId,Value=i-1234567890abcdef0 \
--start-time 2022-10-18T23:18:00 --end-time 2022-10-19T23:18:00
```
The following is example output. Each value represents the maximum CPU utilization percentage for a single EC2 instance.
```
{
"Datapoints": [
{
"Timestamp": "2022-10-19T00:18:00Z",
"Maximum": 0.33000000000000002,
"Unit": "Percent"
},
{
"Timestamp": "2022-10-19T03:18:00Z",
"Maximum": 99.670000000000002,
"Unit": "Percent"
},
{
"Timestamp": "2022-10-19T07:18:00Z",
"Maximum": 0.34000000000000002,
"Unit": "Percent"
},
{
"Timestamp": "2022-10-19T12:18:00Z",
"Maximum": 0.34000000000000002,
"Unit": "Percent"
}
],
"Label": "CPUUtilization"
}
```
# Aggregate statistics across instances
Aggregate statistics are available for instances that have detailed monitoring enabled. Instances that use basic monitoring are not included in the aggregates. Before you can get statistics aggregated across instances, you must [enable detailed monitoring](manage-detailed-monitoring.md#enable-detailed-monitoring) (at an additional charge), which provides data in 1-minute periods.
Note that Amazon CloudWatch cannot aggregate data across AWS Regions. Metrics are completely separate between Regions.
This example shows you how to use detailed monitoring to get the average CPU usage for your EC2 instances. Because no dimension is specified, CloudWatch returns statistics for all dimensions in the `AWS/EC2` namespace.
**Important**
This technique for retrieving all dimensions across an AWS namespace does not work for custom namespaces that you publish to Amazon CloudWatch. With custom namespaces, you must specify the complete set of dimensions that are associated with any given data point to retrieve statistics that include the data point.
**To display average CPU utilization across your instances (console)**
1. Open the CloudWatch console at [https://console.aws.amazon.com/cloudwatch/](https://console.aws.amazon.com/cloudwatch/).
1. In the navigation pane, choose **Metrics**.
1. Choose the **EC2** namespace and then choose **Across All Instances**.
1. Choose the row that contains **CPUUtilization**, which displays a graph for the metric for all your EC2 instances. To name the graph, choose the pencil icon. To change the time range, select one of the predefined values or choose **custom**.
![\[Metrics aggregated across your EC2 instances\]](http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/images/metric_aggregated_instances.png)
1. To change the statistic or the period for the metric, choose the **Graphed metrics** tab. Choose the column heading or an individual value, and then choose a different value.
**To get average CPU utilization across your instances (AWS CLI)**
Use the [get-metric-statistics](https://docs.aws.amazon.com/cli/latest/reference/cloudwatch/get-metric-statistics.html) command as follows to get the average of the **CPUUtilization** metric across your instances.
```
aws cloudwatch get-metric-statistics \
--namespace AWS/EC2 \
--metric-name CPUUtilization \
--period 3600 --statistics "Average" "SampleCount" \
--start-time 2022-10-11T23:18:00 \
--end-time 2022-10-12T23:18:00
```
The following is example output:
```
{
"Datapoints": [
{
"SampleCount": 238.0,
"Timestamp": "2022-10-12T07:18:00Z",
"Average": 0.038235294117647062,
"Unit": "Percent"
},
{
"SampleCount": 240.0,
"Timestamp": "2022-10-12T09:18:00Z",
"Average": 0.16670833333333332,
"Unit": "Percent"
},
{
"SampleCount": 238.0,
"Timestamp": "2022-10-11T23:18:00Z",
"Average": 0.041596638655462197,
"Unit": "Percent"
}
],
"Label": "CPUUtilization"
}
```
# Aggregate statistics by Auto Scaling group
You can aggregate statistics for the EC2 instances in an Auto Scaling group. Note that Amazon CloudWatch cannot aggregate data across AWS Regions. Metrics are completely separate between Regions.
This example shows you how to retrieve the total bytes written to disk for one Auto Scaling group. The total is computed for 1-minute periods for a 24-hour interval across all EC2 instances in the specified Auto Scaling group.
**To display DiskWriteBytes for the instances in an Auto Scaling group (console)**
1. Open the CloudWatch console at [https://console.aws.amazon.com/cloudwatch/](https://console.aws.amazon.com/cloudwatch/).
1. In the navigation pane, choose **Metrics**.
1. Choose the **EC2** namespace and then choose **By Auto Scaling Group**.
1. Choose the row for the **DiskWriteBytes** metric and the specific Auto Scaling group, which displays a graph for the metric for the instances in the Auto Scaling group. To name the graph, choose the pencil icon. To change the time range, select one of the predefined values or choose **custom**.
1. To change the statistic or the period for the metric, choose the **Graphed metrics** tab. Choose the column heading or an individual value, and then choose a different value.
**To display DiskWriteBytes for the instances in an Auto Scaling group (AWS CLI)**
Use the [get-metric-statistics](https://docs.aws.amazon.com/cli/latest/reference/cloudwatch/get-metric-statistics.html) command as follows.
```
aws cloudwatch get-metric-statistics --namespace AWS/EC2 --metric-name DiskWriteBytes --period 360 \
--statistics "Sum" "SampleCount" --dimensions Name=AutoScalingGroupName,Value=my-asg --start-time 2022-10-16T23:18:00 --end-time 2022-10-18T23:18:00
```
The following is example output:
```
{
"Datapoints": [
{
"SampleCount": 18.0,
"Timestamp": "2022-10-19T21:36:00Z",
"Sum": 0.0,
"Unit": "Bytes"
},
{
"SampleCount": 5.0,
"Timestamp": "2022-10-19T21:42:00Z",
"Sum": 0.0,
"Unit": "Bytes"
}
],
"Label": "DiskWriteBytes"
}
```
# Aggregate statistics by AMI
You can aggregate statistics by AMI for your instances that have detailed monitoring enabled. Instances that use basic monitoring are not included in the aggregates. Before you can get statistics aggregated across instances, you must [enable detailed monitoring](manage-detailed-monitoring.md#enable-detailed-monitoring) (at an additional charge), which provides data in 1-minute periods.
Note that Amazon CloudWatch cannot aggregate data across AWS Regions. Metrics are completely separate between Regions.
This example shows you how to determine average CPU utilization for all instances that use a specific Amazon Machine Image (AMI). The average is over 60-second time intervals for a one-day period.
**To display the average CPU utilization by AMI (console)**
1. Open the CloudWatch console at [https://console.aws.amazon.com/cloudwatch/](https://console.aws.amazon.com/cloudwatch/).
1. In the navigation pane, choose **Metrics**.
1. Choose the **EC2** namespace and then choose **By Image (AMI) Id**.
1. Choose the row for the **CPUUtilization** metric and the specific AMI, which displays a graph for the metric for the specified AMI. To name the graph, choose the pencil icon. To change the time range, select one of the predefined values or choose **custom**.
1. To change the statistic or the period for the metric, choose the **Graphed metrics** tab. Choose the column heading or an individual value, and then choose a different value.
**To get the average CPU utilization for an image ID (AWS CLI)**
Use the [get-metric-statistics](https://docs.aws.amazon.com/cli/latest/reference/cloudwatch/get-metric-statistics.html) command as follows.
```
aws cloudwatch get-metric-statistics --namespace AWS/EC2 --metric-name CPUUtilization --period 3600 \
--statistics Average --dimensions Name=ImageId,Value=ami-3c47a355 --start-time 2022-10-10T00:00:00 --end-time 2022-10-11T00:00:00
```
The following is example output. Each value represents an average CPU utilization percentage for the EC2 instances running the specified AMI.
```
{
"Datapoints": [
{
"Timestamp": "2022-10-10T07:00:00Z",
"Average": 0.041000000000000009,
"Unit": "Percent"
},
{
"Timestamp": "2022-10-10T14:00:00Z",
"Average": 0.079579831932773085,
"Unit": "Percent"
},
{
"Timestamp": "2022-10-10T06:00:00Z",
"Average": 0.036000000000000011,
"Unit": "Percent"
}
],
"Label": "CPUUtilization"
}
```