How can I calculate supported maximum PPS (Packets Per Second) of UTM appliance?

In order to calculate the PPS capabilities of a device, the best way is using the throughput ratings on the spec sheets. This way, we can account for PPS with full DPI, and SPI only from actual test results.

EXAMPLE: 

• The NSA 2400 supported UTM throughput is 150Mbps, i.e., the aggregate of bandwidth processing in both directions at the same time
  150 Mbps = 150,000,000 bits =150,000,000/8 = 18,750,000 Bytes
  Default MTU size is 1500, then divide 18,750,000 by 1500 bytes
  18,750,000/1500= 12,500 Packets per second
  So, the NSA 2400, with full DPI, can process 12,500 packets per second.
  
  
• The NSA 2400 supported stateful Inspection  throughput is  775 Mbps, i.e., the aggregate of bandwidth processing in both directions at the same time.
  775 Mbps = 775,000,000 bits
  775,000,000/8 = 96,875,000 bytes
  Default MTU size is 1500, then divide 96,875,000 by 1500 bytes
  96,875,000/1500= 64,584 Packets per second
  So, the NSA 2400, with only stateful Inspection, can process 64,584 packets per second.