Backup Window Calculator

Estimate how long a backup takes from the dataset size and transfer rate, with an optional overhead allowance. Handles megabit and megabyte rates. Calculates in your browser.

Backup window

-

Data moved (with overhead)-
Effective rate-

Show the math

The window is the data to move divided by the sustained transfer rate:

time = data × (1 + overhead) ÷ throughput

Watch the units: throughput in megabits per second (Mb/s) is one eighth of megabytes per second (MB/s). Add overhead to account for protocol, verification or compression passes that slow the real transfer. Calculated entirely in your browser.

What this does

A backup-window calculator estimates how long a backup takes from the dataset size and transfer rate, with an optional overhead allowance.

How to use it

  1. Enter the dataset size.
  2. Enter the transfer rate.
  3. Pick Mb/s or MB/s.
  4. Add overhead and read the window.

How it works

A megabit per second is an eighth of a megabyte per second, so units matter. Overhead pads for protocol, encryption or verification passes.

time = data ÷ transfer rate

Understanding your result

The figure is the raw transfer time, so add the overhead allowance for protocol, encryption, and verification, and confirm it actually fits inside your maintenance window. Watch the units, a megabit is an eighth of a megabyte, and remember the real constraint is often the restore time, not the backup, so test that you can recover within your RTO.

Example

500 GB at 100 MB/s takes about 1 h 25 m before overhead.

Sources & methodology

Last updated .

Frequently asked questions

How is the backup window calculated?

Divide the amount of data by the sustained transfer rate. The result is shown in days, hours, minutes and seconds, with optional overhead added to the data moved.

Mb/s or MB/s, does it matter?

Very much. A megabit per second (Mb/s) is an eighth of a megabyte per second (MB/s), so a link quoted in megabits is far slower than the same number in megabytes. The calculator lets you pick the right unit.

What should I put for overhead?

Use it to account for protocol, encryption or verification passes that slow the real transfer, a few to twenty percent is common. Leave it at zero for a best-case estimate.