A computer-implemented method sizes a Storage Area Network (SAN) storage migration. One or more processors determine Input/output Operations Per Second (IOPS) and throughput of hardware devices operatively coupled to a target Storage Area Network (SAN) prior to a SAN migration from a source SAN to the target SAN. One or more processors determine an estimated time and size of the SAN migration based on the IOPS and the throughput of the hardware devices. One or more processors then configure transmission resources available to the source SAN to comport with the estimated time and size of the SAN migration.