Backup Size Estimator
Estimate full and incremental backup sizes based on data volume and change rate.
Inputs
Percentage of the full backup's data that changes per day
e.g. 7 for a weekly full backup cycle
Typically days_between_fulls − 1 for daily incrementals
Total Storage (Full + Incrementals)
590.00GB
Total Storage (Full + Differentials)
815.00GB
Daily Change Volume
15.000GB
Storage Saved Using Incrementals vs Differentials
225.00GB
Step by step
Values used
Full Backup Size = 500 GB; Daily Data Change Rate = 3 %; Days Between Full Backups = 7; Number of Incremental Backups per Cycle = 6
Total storage with incrementals
total = full + (daily_change% × full × num_incrementals)
Total storage with differentials
total = full + Σ(daily_change% × full × day) for day = 1 to num_incrementals
Total Storage (Full + Incrementals)
= 590.00 GB
Total Storage (Full + Differentials)
= 815.00 GB
Daily Change Volume
= 15.000 GB
Storage Saved Using Incrementals vs Differentials
= 225.00 GB
How it works
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
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.