Compression ratio calculator
Ratio and percentage saved are two ways of saying the same thing, and people mix them up constantly.
Compression ratio
4.0000
- Space saved
- 75.000 %
- Bits per original byte
- 2.0000
- Corpus after compression
- 2.500
- Storage saved
- 7.500
Show the working
- Original size = 1000
- Compressed size = 250
- Total data to store = 10
- Compression ratio = 1000 / 250 = 4
- Space saved = (1 - 250/1000) * 100 = 75
- Bits per original byte = 4 > 0 ? 8 / 4 : 0 = 2
- Corpus after compression = 4 > 0 ? 10 / 4 : 0 = 2.5
- Storage saved = 10 - 2.5 = 7.5
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- ratio = original / compressed
- saving = 1 - compressed / original
A 4:1 ratio is a 75% saving. A 75% ratio is not a thing — check which one a vendor means.