Compression Ratio Calculator
Turn measured sizes before and after compression into a ratio and the space saved.
In short
Formula: Ratio = S_uncompressed / S_compressed; Saved = S_uncompressed - S_compressed
What this calculator does
Compression ratio as defined in data-management practice: uncompressed size divided by stored size, expressed as n : 1. Space saved is the difference; the saving share is that difference over the uncompressed size. A stored size larger than the original is reported as expansion rather than hidden.
Use it to turn Size before compression, Size after compression into a checked result you can compare, copy, or rerun with different assumptions.
The page shows the formula, a numeric worked example, and the assumptions that affect this professional & industry calculation.
Inputs and what they mean
- Size before compression
- — Uncompressed size of the data..
- Size after compression
- — Size actually stored once compressed..
How to use it
- Enter your own figures — the calculator never fills in a rate, price or benchmark for you.
- Press Calculate to see the result.
- Read the formula, variables, assumptions and source below the result before you rely on it.
Formula
Ratio = S_uncompressed / S_compressed; Saved = S_uncompressed - S_compressed.
Inputs used: Size before compression, Size after compression.
Edge handling: Size before compression is required.; Size before compression cannot be negative.; Size before compression must be no more than 1000000000000.; Size after compression is required.; Size after compression cannot be negative..
Worked example
1,200 GB stored in 310 GB
- Start with Size before compression: 1200, Size after compression: 310.
- Apply the method: Ratio = S_uncompressed / S_compressed; Saved = S_uncompressed - S_compressed.
- Your own measured sizes before and after compression.
Reading the result
The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.
Limitations and assumptions
- Inputs outside the supported range are rejected rather than forced into a result.
- The result depends on the values you enter for this compression ratio calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.
Reference: DAMA International — DAMA-DMBOK — Data Management Body of Knowledge
Last reviewed:
Common questions
Where does this formula come from?
DAMA-DMBOK data storage, integration and data-quality practice: volume growth is projected from measured history under a stated model; compression ratio is uncompressed size divided by stored size; throughput is volume processed divided by elapsed time; data currency (freshness) is the age of the data at the time it is used, measured against a stated requirement. See the source link on this page.
What kind of calculation is this?
The uncompressed size as a multiple of the stored size, with the space saved and its share. Check the formula, example, and limitations on this page before using the result for a real professional & industry decision.
What are its limits?
Arithmetic over the figures entered — it cannot tell whether the underlying metering, logs or job records are complete. A figure from one run or one period is a weak description of ongoing behaviour. A ratio measured on one sample does not transfer to other data. Compression and decompression time and cost are not considered.
How do I use the Compression Ratio Calculator?
Enter the required values for Size before compression, Size after compression. The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.
What formula does the Compression Ratio Calculator use?
Ratio = S_uncompressed / S_compressed; Saved = S_uncompressed - S_compressed The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone. Check the formula, example, and limitations on this page before using the result for a real professional & industry decision.
Can the Compression Ratio Calculator be used for exact decisions?
Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.
Formula, source and verification
The uncompressed size as a multiple of the stored size, with the space saved and its share.
The question it answers: How large will this data store get, how much does compression save, and what does the retention policy cost?
The formula
Ratio = S_uncompressed / S_compressed; Saved = S_uncompressed - S_compressed
- Su — Size before compression
- (GB). Uncompressed size measured by the user.
- Sc — Size after compression
- (GB). Size actually stored.
Units: Gigabytes in; a dimensionless ratio, gigabytes saved and a percentage out. Both sizes must use the same unit.
What kind of calculation this is
Deterministic formula. The same inputs always give the same answer. The maths is fixed and does not depend on judgement.
Method
Compression ratio as defined in data-management practice: uncompressed size divided by stored size, expressed as n : 1. Space saved is the difference; the saving share is that difference over the uncompressed size. A stored size larger than the original is reported as expansion rather than hidden.
Assumptions built into the result
- Mathematical: All the figures entered cover the same measurement period.
- Mathematical: Volumes, records and runs are counted consistently with the definitions the team has written down.
- Mathematical: Both sizes are measured the same way, including or excluding metadata consistently.
Figures this calculator will never guess for you
- No target, benchmark, industry average or typical figure is supplied for any value.
- A definition is never presented as a goal: the freshness formula is not a freshness target, and the growth formula is not a forecast of what growth should be.
- No compression ratio is assumed for any algorithm, format or data type.
Limitations
- Arithmetic over the figures entered — it cannot tell whether the underlying metering, logs or job records are complete.
- A figure from one run or one period is a weak description of ongoing behaviour.
- A ratio measured on one sample does not transfer to other data.
- Compression and decompression time and cost are not considered.
Source and version
- Standard or reference
- DAMA-DMBOK — Data Management Body of Knowledge — DAMA International (DAMA-DMBOK data storage, integration and data-quality practice: volume growth is projected from measured history under a stated model; compression ratio is uncompressed size divided by stored size; throughput is volume processed divided by elapsed time; data currency (freshness) is the age of the data at the time it is used, measured against a stated requirement.)
- Published source
- DAMA International — DMBOK
- Formula version
- Version 1
- Verification
- Reviewed against the cited source on
- How much weight the source carries
- Standards or government
- Applies to
- Currency
- The result is a ratio or index, so it does not depend on currency.
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