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Backup Window Bandwidth Calculator

Work out backup window bandwidth instantly with clear inputs, formula shown and shareable results.

About Backup Window Bandwidth Calculator

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.

Formula

Backup bandwidth

transferred = data / compression ratio; goodput = bits / window seconds; link = goodput / usable share

Worked example

With the default values below, Backup Window Bandwidth Calculator returns Link speed required of 317.5. Change any input above and every figure here is recalculated in your browser.

Inputs used

Data to transferminimum 0.001 GB
2,000 GB
Backup windowaccepts 0.1–24 h
8 h
Usable share of the linkaccepts 1–100 %
70 %
Compression ratioaccepts 1–50 x
2.5 x

Results

Link speed required
317.5 Mbps
Goodput needed
222.2 Mbps
Bytes actually transferred
745.06 GiB
Window needed on a 1 Gbps link
2.54 h

Step by step

  1. 1Values used
  2. 2Backup bandwidth
  3. 3Link speed required= 317.5 Mbps
  4. 4Goodput needed= 222.2 Mbps
  5. 5Bytes actually transferred= 800,000,000,000
  6. 6Window needed on a 1 Gbps link= 2.54 h

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why is only 70 percent of the link usable?

TCP overhead, ACK traffic, other production flows and imperfect parallelism. Sustained single-stream transfers over WAN links often achieve far less without tuning.

What if the window cannot be met?

Switch to incremental or changed-block-only backups, which reduce the data volume by an order of magnitude, rather than buying a bigger link.

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