AWS bill line item
CW:MetricMonitorUsage
The per-metric-per-month charge for every unique custom metric (and dimension combination) published to CloudWatch, whether from your own application, embedded metric format logs, or detailed instance monitoring.
CloudWatch custom metrics
Verified against official AWS documentation last checked
Why it shows up
Custom metrics are billed per unique dimension combination, not per metric name, so tagging a metric with a high-cardinality dimension (a request ID, a user ID, a container ID) can generate thousands of billable metric series from what looks like a single metric.
Detailed monitoring and the CloudWatch embedded metric format both bill through this same usage type, so a spike can come from infrastructure nobody thought of as "custom metrics" at all.
How to cut it
- Audit namespaces for unused or experimental metrics and delete the ones no dashboard or alarm references anymore.
- Avoid high-cardinality dimensions on custom metrics; aggregate before publishing.
- Only enable higher-resolution monitoring where it matters. Basic monitoring is free.
- Batch metric-publishing calls and review agent configs for metrics nobody ever looks at.
$0.30 per metric per month (first 10,000 custom metrics) — us-east-1, as of 2026-07
How to read a usage type
The colon in CW:MetricMonitorUsage doesn't introduce an instance type the way it does in a code like BoxUsage:m5.large. This code carries no region or direction token either, so there's nothing to break down here.
Source
Source: AWS docs →Found CW:MetricMonitorUsage on your own bill?
Drop your Cost Explorer CSV into the AWS Bill Analyzer. It'll flag line items like this one on your own bill and link straight back to the fix.
Analyze your own bill →The invoice is a lagging signal.
A monthly invoice tells you what already happened. CostMon builds a daily baseline, so a spike stands out while you can still act on it.