How to use the backup storage calculator
Enter the protected dataset size in GB, the number of full copies kept, the average daily change percentage, and the number of days of incremental backups. Set the final percentage to the fraction of uncompressed data expected to remain after compression.
Read the compressed-size percentage correctly
A stored-size value of 60% means a 500 GB backup contributes about 300 GB after compression. A value of 100% means no size reduction. If your measured data grows when stored, a value above 100% can represent that overhead.
Worked example
For 500 GB of data, four full copies, 5% changed each day, 26 incremental days, and a 60% stored-size ratio: full copies use 500 × 4 × 0.60 = 1,200 GB; increments use 500 × 0.05 × 26 × 0.60 = 390 GB; the estimated total is 1,590 GB.
What the estimate leaves out
This model assumes each day’s changed amount is stored once and compresses at the same rate as the full copies. It does not model deduplication, replicas, snapshots, metadata, failed jobs, immutable retention, or provider-specific billing units. Backup products also differ in which resource types use incremental backups; verify the behavior and actual storage in your provider’s documentation and console.
Sources & assumptions
Verified 2026-10-28. This is a planning estimate based on the five visible inputs, not a provider quote or repository measurement.
Official reference
- AWS Backup plans (incremental behavior depends on supported resource type)
