How to calculate the throughput performance of FortiGate-VMUL?

Hello,

You may find command "get system performance status" useful. It will return how much traffic is processed by FortiGate:

https://community.fortinet.com/t5/FortiGate/Technical-Tip-Explaining-the-get-system-performance-status/ta-p/228275

Generally throughput will positively correlate with the number of vCPU, however the results may depend how benchmark test is conducted.

Throughput on a FortiGate-VM isn't determined by vCPU count alone. It also depends on traffic type, enabled security features, session volume, and the underlying hardware.

The best approach is to run performance tests that match your real workload. It's similar to a mauricette calculator for work hours: the final result depends on multiple factors, not just one input. More vCPUs can help, but actual throughput needs to be measured rather than estimated.

There isn't a simple formula that converts vCPU count into FortiGate-VMUL throughput. The actual performance depends on traffic patterns, packet sizes, enabled security services (IPS, Application Control, SSL inspection, etc.), hypervisor settings, and the underlying hardware. Even Fortinet notes that benchmark results can vary significantly depending on the test environment.

The best approach is to measure throughput under workloads that resemble your production traffic using tools such as iPerf and the get system performance status command. Real-world testing will give much more accurate results than trying to estimate performance from vCPU count alone.