Calculated metric

Calculated metric creates a new number from current readings that already exist.

1. Add this check.

2. Enter Formula, Unit and optionally Warning at or Critical at.

3. Add one row under Sources for each required value.

4. Under Variable, enter a unique lowercase name, for example a or ram_total.

5. Under Metric series, select the area integration, extended, resource or service, and then the specific Metric ID entry. The interface displays matching device and reading labels.

6. Set Maximum age in seconds; default 300, allowed range: 15 to 86.400.

7. Test and save.

Measurement series	Value used
integration	Value from an additional check
extended	Value from an extended resource measurement
resource	Percentage value from a basic resource measurement
service	Response time from a ping, TCP or web check

Example: Two sources a and b can be added with a + b. Addition, subtraction, multiplication, division, modulo, parentheses, signs, and min, max, abs and round are supported. Variable names start with a lowercase letter and contain lowercase letters, digits or underscores. A maximum of 20 sources is possible.

Missing, paused, dependency-blocked, unactivated or outdated sources do not supply a valid calculated value. The maximum age does not extend the source check’s normal freshness deadline. An error such as division by zero is reported as a check result. Destination address and Port are also present in the shared input form for this check; the calculation uses the selected saved readings.