Compression Ratio
Calculate the compression ratio and space savings between original and compressed data sizes.
About Compression Ratio
The compression ratio expresses how many times smaller a compressed file is compared to its original, calculated by dividing the original size by the compressed size — a ratio of 4:1 means the compressed file is a quarter of the original. Space savings, expressed as a percentage, is derived from the ratio as one minus its reciprocal, giving an intuitive figure for how much storage or bandwidth was reclaimed.
Formula
Compression ratio and savings
ratio = original_size / compressed_size; savings = (1 − 1/ratio) × 100%
- S_o
- Original size
- S_c
- Compressed size
Worked example
With the default values below, Compression Ratio returns Compression Ratio of 4:1. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Original Sizeminimum 0.01 MB
- 1,000 MB
- Compressed Sizeminimum 0.01 MB
- 250 MB
Results
- Compression Ratio
- 4:1
- Space Savings
- 75.00%
- Space Saved
- 750.00 MB
- Ratio (decimal)
- 4.000
Step by step
- 1Values used
- 2Compression ratio and savings
- 3Compression Ratio= 4:1
- 4Space Savings= 75.00
- 5Space Saved= 750.00 MB
- 6Ratio (decimal)= 4.000
Assumptions and limits
- The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
What does a compression ratio of 4:1 mean?
A 4:1 ratio means the original file is four times larger than the compressed version — equivalently, the compressed file occupies 25% of the original's storage or transfer footprint, a 75% space saving.
Why do some files compress better than others?
Compression algorithms exploit redundancy and predictable patterns in data. Text and uncompressed formats (BMP, WAV, raw logs) usually compress well because they contain repeated structures, while already-compressed formats (JPEG, MP4, ZIP) compress poorly because their redundancy has already been removed.
Is a higher compression ratio always better?
Not necessarily — very high ratios from lossy compression can degrade quality (images, audio, video), and higher-ratio algorithms often demand more CPU time to compress and decompress, so the right choice balances size, quality, and processing cost for the use case.