Backup Size Estimator
Estimate full and incremental backup sizes based on data volume and change rate.
About Backup Size Estimator
A full backup captures everything; incremental backups capture only what changed since the previous backup (full or incremental), so their combined size grows linearly with the daily change rate. Differential backups instead capture everything changed since the last full backup, so each successive differential grows larger as the cycle progresses, trading more storage for simpler, faster restores (only the last full + last differential are needed, versus a full + every incremental in sequence).
Formulas
Total storage with incrementals
total = full + (daily_change% × full × num_incrementals)
- F
- full backup size
- c
- daily change rate as a fraction
- n
- number of incremental backups
Total storage with differentials
total = full + Σ(daily_change% × full × day) for day = 1 to num_incrementals
- F
- full backup size
- c
- daily change rate as a fraction
- n
- number of differential backups taken
Worked example
With the default values below, Backup Size Estimator returns Total Storage (Full + Incrementals) of 590.00. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Full Backup Sizeminimum 0 GB
- 500 GB
- Daily Data Change Rateaccepts 0–100 %
- 3 %
- Days Between Full Backupsminimum 1
- 7
- Number of Incremental Backups per Cycleaccepts 0–1,000
- 6
Results
- Daily Change Volume
- 15.000 GB
- Total Storage (Full + Incrementals)
- 590.00 GB
- Total Storage (Full + Differentials)
- 815.00 GB
- Storage Saved Using Incrementals vs Differentials
- 225.00 GB
Step by step
- 1Values used
- 2Total storage with incrementals
- 3Total storage with differentials
- 4Total Storage (Full + Incrementals)= 590.00 GB
- 5Total Storage (Full + Differentials)= 815.00 GB
- 6Daily Change Volume= 15.000 GB
- 7Storage Saved Using Incrementals vs Differentials= 225.00 GB
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 3 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
What is the difference between incremental and differential backups?
Incremental backups capture only the changes since the most recent backup of any type (full or incremental), keeping each backup small. Differential backups capture all changes since the last full backup, so each one grows larger over the cycle but restoration only needs the full plus the single latest differential.
Which strategy uses less storage?
Incremental backups almost always use less total storage than differential backups over the same cycle, because differentials repeatedly re-capture changes that earlier differentials in the same cycle already recorded.
Which strategy restores faster?
Differential backups restore faster because you only need the last full backup plus the single most recent differential. Incremental restores require replaying the full backup plus every incremental in sequence since it, which takes longer and has more failure points.