CloudWatch Dashboard to manage & monitor a budget

Question

In CloudWatch dashboard, is it possible to use math expressions (e.g. based on EstimatedCharges or some other metric) to create a metric that shows a budget, with month-to-month cloud spending gradually deducted from that budget?

Example: Suppose there is a starting budget of $1000. The cloud spend is $200 in the first month, and $100 in the second. Hence, the metric needs to have an initial value of $1000, which decreases to $800 at the end of the first month, and $700 at the end of the second month.

Can I use CloudWatch Dashboards with math expressions for this, or would other services be needed? e.g. QuickSight, Lambda?

Answer

This graph would be approximately what you need, where you are plotting ```1000 less the running total of your estimate spend```.

```
{
    "metrics": [
        [ { "expression": "1000 - RUNNING_SUM(monthly)", "label": "Expression1", "id": "budget" } ],
        [ "AWS/Billing", "EstimatedCharges", "Currency", "USD", { "id": "monthly", "visible": false } ]
    ],
    "view": "timeSeries",
    "stacked": false,
    "region": "us-east-1",
    "stat": "Maximum",
    "period": 2592000
}
```

However, it is difficult to get exact value of spend in a month.  To get exact values you would be better off querying [AWS Cost Explorer](https://aws.amazon.com/aws-cost-management/aws-cost-explorer/).  CloudWatch Dashboards has a [Custom Widget](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/add_custom_widget_samples.html) feature that comes with a simple **AWS Cost Explorer report**. It would be relatively easy to adapt the code in that to display what you need.

Answer

Your use case might be met using AWS Budgets? For more details see https://aws.amazon.com/aws-cost-management/aws-budgets/.

CloudWatch Dashboard to manage & monitor a budget

Relevant questions

Scale errors on simple CloudWatch Dashboard

Create dynamic cross account CloudWatch Dashboard