Enter the port speed and the number of ports into the calculator to determine the switching capacity of a network switch. Switching capacity is typically quoted as an aggregate full‑duplex value (Tx + Rx), and the calculator provides the total switching capacity in gigabits per second (Gbps).

Switching Capacity Calculator

Enter any 2 values to calculate the missing variable (assumes full‑duplex by default)

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Switching Capacity Formula

The following formula is commonly used to estimate the switching capacity (switching fabric/backplane) of a network switch when all ports run at the same line rate and full‑duplex operation is assumed (transmit + receive).

SC = PS * PC * 2

Variables:

  • SC is the switching capacity (Gbps)
  • PS is the port speed (Gbps)
  • PC is the port count (number of ports)

To calculate the switching capacity, multiply the port speed by the number of ports on the switch, then multiply by 2 for full‑duplex (Tx + Rx). (For a one‑direction aggregate figure, use SC = PS × PC.)

What is Switching Capacity?

Switching capacity refers to the maximum aggregate throughput the switch fabric can handle, typically quoted by vendors as the sum of all ports’ line rates in both directions (full‑duplex), and often expressed in gigabits per second (Gbps) or terabits per second (Tbps). This is a key specification for understanding whether the switch backplane can carry simultaneous traffic across many ports (note that it is different from packet forwarding rate, which is usually specified in packets per second).

How to Calculate Switching Capacity?

The following steps outline how to calculate the Switching Capacity.

  1. First, determine the port speed (PS) in gigabits per second (Gbps).
  2. Next, determine the number of ports on the switch (PC).
  3. Next, gather the formula from above = SC = PS * PC * 2 (for full‑duplex).
  4. Finally, calculate the Switching Capacity (SC) in gigabits per second (Gbps).
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Port speed (PS) = 1 Gbps

Number of ports (PC) = 48

Switching Capacity (SC) = 1 × 48 × 2 = 96 Gbps (full‑duplex).