Backup Window & Bandwidth Calculator

Assumptions

• TB uses decimal capacity: 1 TB = 10^12 bytes.
• The reduction ratio is source data divided by the data actually transferred. A ratio of 2 means half the changed data is transferred.

Important notes

• Model the initial full backup, synthetic full backups, snapshots, database logs and concurrent restore jobs separately. The result is an average bandwidth requirement within the entered window, not a guaranteed transfer rate.

Standards and sources

• NIST SP 800-34 Rev. 1 Contingency Planning Guide

Verified: 2026-09-05

Calculation method

Changed data (TB) = dataset size × daily change % / 100. Transferred data = changed data / reduction ratio. Required bandwidth (Mbps) = transferred data × 10^12 × 8 / (window hours × 3600 × efficiency % / 100 × 10^6). MB/s = Mbps / 8.

Worked example

Planning example: 20 TB of data, 5% daily change, a reduction ratio of 2, an 8-hour window and 80% efficiency. Changed data is 1 TB; transferred data is 0.5 TB; average required bandwidth is approximately 173.61 Mbps (21.70 MB/s).

Scope and limitations

This model uses daily changed data and does not size the initial full backup. Check full and synthetic backups, logs, concurrent tasks and actual source/target throughput separately. This example is not a throughput guarantee.