Incremental Backup Size Calculator

Work out incremental backup size instantly with clear inputs, formula shown and shareable results.

About Incremental Backup Size Calculator

File-level incrementals copy every byte of any file whose timestamp changed, so a one-byte edit to a 10 GB database file copies all 10 GB. Block-level or changed-block tracking copies only the differing extents, which for large mutable files reduces the incremental by an order of magnitude — the main reason snapshot-based backup outperforms file-based tools on databases and VM images.

Formula

Incremental size

file level = dataset x changed file share; block level = file level x share differing within each file

Worked example

With the default values below, Incremental Backup Size Calculator returns Incremental backup size of 15.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Dataset sizeminimum 0.001 GB: 2,000 GB
Files changed since the last backupaccepts 0.001–100 %: 5 %
Change tracking granularityone of Whole file, Changed blocks only: Changed blocks only
Share of each changed file that actually differsaccepts 0.1–100 %: 15 %

Results

Incremental backup size: 15.00 GB
Size with whole-file tracking: 100.00 GB
Size with block-level tracking: 15.00 GB
Saving from block-level tracking: 85.0%

Step by step

1Values used
2Incremental size
3Incremental backup size= 15.00 GB
4Size with whole-file tracking= 100.00 GB
5Size with block-level tracking= 15.00 GB
6Saving from block-level tracking= 85.0

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 file-level so much worse for databases?

Because database files are huge and constantly touched. Every backup copies the entire file even though a tiny fraction of blocks changed.

Does deduplication help further?

Yes, especially across similar systems. Global deduplication can cut backup storage several times more by storing each unique block once for the whole estate.