Backup Storage Size Calculator

Estimate the total storage needed for backups considering full/incremental schedules, retention periods, compression, and deduplication ratios.

Total Data Size to Back Up (GB)

Daily Change Rate (%) Percentage of total data that changes each day (typical: 2–10%)

Full Backup Frequency (days) How often a full backup is taken (e.g. 7 = weekly)

Retention Period (days) How long backups are kept before deletion

Compression Ratio Storage saved by compression (e.g. 1.5 means data compresses to 1/1.5 of original; typical: 1.2–2.0)

Deduplication Ratio Storage saved by deduplication (e.g. 2.0 means half the storage needed; typical: 1.5–5.0)

Number of Backup Copies (e.g. 3-2-1 rule) Total copies including primary and offsite (3-2-1 rule recommends 3)

Storage Overhead (%) Extra buffer for metadata, catalog, and unexpected growth (typical: 10–20%)

Number of full backups = ⌈Retention Days ÷ Full Backup Frequency⌉

Number of incremental backups = Retention Days − Number of Full Backups

Daily incremental size = Total Data Size × (Daily Change Rate ÷ 100)

Raw full backup storage = Number of Full Backups × Total Data Size

Raw incremental storage = Number of Incrementals × Daily Incremental Size

Total raw storage = Raw Full Storage + Raw Incremental Storage

Reduction factor = Compression Ratio × Deduplication Ratio

Reduced storage = Total Raw Storage ÷ Reduction Factor

Storage with overhead = Reduced Storage × (1 + Overhead% ÷ 100)

Total required storage = Storage with Overhead × Number of Copies

Incremental backups capture only data changed since the last backup (full or incremental).
A full backup is taken at the start of each cycle; the remaining days in the cycle use incrementals.
Compression and deduplication ratios are applied uniformly across all backup sets.
Typical daily change rates range from 2–10% for enterprise workloads (Veeam Best Practices, 2023).
Typical compression ratios: 1.2–2.0×; deduplication ratios: 1.5–5.0× depending on data type.
The 3-2-1 backup rule recommends 3 copies on 2 different media with 1 offsite (NIST SP 800-34).
Storage overhead of 10–20% is recommended to account for backup catalog, metadata, and growth spikes.
All calculations assume consistent data change patterns; actual usage may vary.
Reference: Veeam Backup & Replication Best Practices Guide; NIST SP 800-34 Rev. 1 (Contingency Planning).

In the network