How to estimate data migration time

Start with the amount of data and the sustained transfer rate, not only the advertised link speed. The theoretical formula is data in bits divided by bits per second.

Add migration overhead

Validation, encryption, many small files, storage limits, retries and competing traffic can extend a migration. Measure sustained throughput when possible and leave operational headroom.

Planning from a deadline

If the migration must finish inside a fixed window, work backwards from the deadline to calculate the minimum bandwidth.

See the transfer-time formula and real-world throughput factors.