Qualys Scanner Capacity Calculator

The Qualys Scanner Capacity Calculator helps you estimate the scanner resources needed to complete your network scans within a target time. Based on your scan workload, scanner configuration, and performance settings, it estimates the number of scanners required, the recommended number of scan jobs, and the expected scan duration.

The calculator provides planning estimates only. Actual scan performance may vary depending on factors such as network conditions, scan configuration, target responsiveness, and available scanner resources.

The Scanner Capacity Calculator is a lightweight, single-page web application that requires no installation or server. Once the page loads, you can use it offline.

Benefits

The scanner capacity calculator allows you to:

Estimate the scanning capacity of a Qualys scanner.
Determine the optimal number of scan jobs for maximum parallelism.
Estimate the number of scanners required to complete a scan within a specified time window.
Compare different scanner pool sizing strategies.
Plan scanner deployments before scheduling large-scale scans.

How Does it Calculate the Capacity?

The calculator estimates scanner capacity by evaluating CPU and memory resources. The effective scanner capacity is determined by the lower of the CPU-based and memory-based capacities. For virtual and containerized scanners, an additional capacity adjustment is applied.

Key Concepts

The following table describes the key concepts used in the Scanner Capacity Calculator workflow and capacity estimation process:

Term	Description
Slice	A scan job is divided into one or more slices, each covering up to P target IPs. Total slices = ceil(Target IPs / P) Each slice is dispatched to a scanner as a unit of work
Job	A job is a configured scan in Qualys (target list + scan profile). A job dispatches one slice per scanner at a time. To run more slices in parallel on the same scanner, split large jobs into multiple smaller jobs.
Round	A round is one parallel wave of slice execution across the entire scanner pool. Rounds = ceil(Total Slices / (Scanners x Max Slices per Scanner))
Burst	A burst is a single pass in which all scanners process their assigned slices in parallel. When all slices fit in a single burst, all target IPs are scanned simultaneously. Bursts = ceil(Total Slices / (Scanners x Max Slices per Scanner))
Concurrent Jobs Cap	Since a scanner runs one slice per job, the effective max slices per scanner = min(capacityMaxJobs, ConcurrentScansAndMaps). When the limit is below what the hardware could run, a bigger spec will not reduce time — only raising the limit or adding scanners helps. WAS uses the Concurrent WAS Scans limit instead.
Capacity Units	Scanner capacity is estimated from hardware specs: Virtual Internal: CPU MHz x vCPUs x RAM factor x virtual penalty (0.6) x HT penalty (0.6 if enabled) Virtual Perimeter: CPU MHz x vCPUs x RAM factor (no virtual penalty) Physical 6120-B1 (NVXE): Fixed at 1,245 units Physical 6120-A1 (NVX): Fixed at 1,040 units Capacity per slice: 100 units (ML Scaling OFF) or 300 units (ML Scaling ON).

Last updated: July, 2026