Work out backup window bandwidth instantly with clear inputs, formula shown and shareable results.
A backup window is a hard deadline, so the required rate is compressed data divided by the window, then divided again by the share of the link you can actually use — protocol overhead, disk contention and other traffic all take a cut. Compression is the cheapest lever because it reduces bytes before they reach the wire.
Backup bandwidth
transferred = data / compression ratio; goodput = bits / window seconds; link = goodput / usable share
TCP overhead, ACK traffic, other production flows and imperfect parallelism. Sustained single-stream transfers over WAN links often achieve far less without tuning.
Switch to incremental or changed-block-only backups, which reduce the data volume by an order of magnitude, rather than buying a bigger link.