Data Center Bandwidth Calculator

Aggregation bandwidth is total access-layer bandwidth divided by the oversubscription ratio, so a higher ratio directly shrinks the reported figure. A 3:1 ratio assumes only about a third of access-layer capacity is needed upstream at once, which holds for typical mixed workloads but understates real demand for storage replication or AI training clusters where NICs run near full line rate continuously.

ToR switch count is total server ports (server count × NICs per server) divided by a fixed 48 server-facing ports per switch, rounded up. Spine switch count then takes each ToR's 4 assumed uplinks, sums them across all ToRs, and divides by a fixed 32 ports per spine switch, with a floor of 2 spines for redundancy — both are generic hardware assumptions, not your specific switch model's real port counts.

It's the theoretical maximum throughput across the spine-leaf fabric if you split all servers into two halves and had every server in one half talk to a server in the other half simultaneously — computed as ToR switch count × uplinks per ToR × port speed. It's a fabric design metric for evaluating non-blocking capacity, not a number you'd expect to see in day-to-day utilization graphs.

The monthly transfer figure multiplies effective bandwidth (access bandwidth adjusted by your average utilization percentage) by a fixed conversion factor of roughly 324 to get terabytes per month, assuming that utilization level holds constant around the clock. Real traffic is bursty rather than flat, so actual transfer volumes can differ substantially from this steady-state estimate depending on your workload's time-of-day and day-of-week patterns.