Deduplication & Compression Ratio Calculator
Enter your Logical Data Size and unit, then set your Deduplication Ratio and Compression Ratio — or use a workload preset. Click Calculate Savings and the results panel shows physical storage required, total space saved, and the combined data reduction ratio: the multiplier that tells you how far your physical hardware goes.
Data Reduction Parameters
Data Reduction Results
Combined Ratio
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Physical Footprint
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Space Saved
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Savings %
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Formula:
Combined Ratio = Dedup Ratio × Compression Ratio
Physical Footprint = Logical Size ÷ Combined Ratio
Space Saved = Logical Size − Physical Footprint
Typical Data Reduction Ratios by Workload
| Workload Type | Dedup Ratio | Compression Ratio | Combined (typical) | Notes |
|---|---|---|---|---|
| Backup / Archive | 10–20:1 | 1.5–2:1 | 15–40:1 | Best case; repeated versions of same files |
| Virtual Machines (VDI) | 3–5:1 | 1.5–2:1 | 5–10:1 | Shared OS images across many VMs |
| Oracle / SQL Databases | 2–5:1 | 2–4:1 | 4–10:1 | Highly repetitive row/index structures |
| File Shares / Documents | 2–4:1 | 1.5–3:1 | 3–8:1 | Office files and text compress well |
| 2–3:1 | 1.5–2:1 | 3–5:1 | Repeated attachments benefit from dedup | |
| Mixed Enterprise | 2–3:1 | 1.5–2:1 | 3–5:1 | HPE/NetApp vendor typical claim |
| Video / Images / Media | 1:1 | 1:1 | 1:1 | Pre-compressed; no reduction possible |
Understanding Data Reduction
Data deduplication and compression are the two primary software-based data reduction techniques used in modern storage arrays. Deduplication eliminates redundant blocks of data across the entire dataset — for example, if 50 virtual machines share the same OS image, the underlying blocks are stored only once. Compression reduces the size of unique data blocks by encoding repetitive byte patterns more efficiently. Related: Plan usable storage capacity.
The two techniques are complementary and most enterprise arrays apply both. Deduplication is typically performed inline (before data is written) or post-process (after writing). Inline dedup reduces write I/O but requires more CPU. Post-process dedup avoids impacting write latency but temporarily requires extra capacity. Understanding your workload's data reduction potential before purchasing storage can significantly reduce hardware costs. Check out our estimate storage cost per TB.
Effective data reduction ratios vary dramatically by workload type. Backup data — which contains many repeated versions of the same files — often achieves 20:1 or greater combined ratios. Virtual desktop infrastructure (VDI) with hundreds of identical OS images typically achieves 5–10:1. Databases with frequently updated rows may achieve 3–5:1. Video, images, and already-compressed files achieve near 1:1 since the data is already entropy-maximized and cannot be reduced further. See also: StorageMath storage tools.
Key Concepts
Deduplication: Identifies and eliminates identical data blocks across the dataset. A 3:1 ratio means 3TB of logical data is stored in 1TB of physical space by referencing duplicate blocks rather than storing them multiple times.
Compression: Reduces the size of unique data blocks using encoding algorithms (LZ4, ZLIB, etc.). A 1.5:1 ratio means 1.5TB of data is compressed to 1TB on disk.
Combined Ratio: The product of both ratios. A 2:1 dedup and 1.5:1 compression gives a 3:1 combined ratio — meaning 3TB of data occupies only 1TB of physical storage.
Vendor Claims vs Reality: Vendors often advertise best-case ratios. Use conservative estimates (mixed enterprise: 2–3:1 combined) for capacity planning unless your workload is known to be dedup-friendly.