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Compression Ratio Calculator
Converts between compression ratio, percentage saved and bits per byte, and works out the bandwidth and transfer time a saving buys.
Developer
Nothing uploaded
No sign-up
Free, unlimited
Optional — turns the saving into monthly bandwidth.
Optional — turns the saving into time.
Enter your figures and press Calculate.
In short
Compression Ratio Calculator is a free online tool on inputtesthub.com that converts between compression ratio, percentage saved and bits per byte, and works out the bandwidth and transfer time a saving buys. It needs no account, no download and no payment, and there is no daily usage limit. Everything is processed inside your own browser, so the data you paste is never uploaded to a server.
How to use the Compression Ratio Calculator
- Enter the size before and after.
- Add transfers per month to see the bandwidth.
- Add a connection speed to see the time.
About the Compression Ratio Calculator
The Compression Ratio Calculator converts between compression ratio, percentage saved and bits per byte, and works out the bandwidth and transfer time a saving buys. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.
What people use it for
- Turning "3:1" into a percentage, or the reverse.
- Working out the monthly bandwidth a compression change saves.
- Comparing two compressors quoted in different units.
Details
| Ratio | Original ÷ compressed, written as 3:1 |
|---|---|
| Space saving | 1 − compressed ÷ original, written as 67% |
| Bits per byte | 8 means no compression; text usually lands near 2 |
| They are reciprocals | 2:1 is the same as 50% saved |
The maths behind it
This tool uses compression ratio = original ÷ compressed, space saving = 1 − compressed ÷ original, and bits per byte = 8 × compressed ÷ original. Every intermediate value is shown on screen, so the result can be checked by hand.
The three figures here are the same fact in three notations, and papers, product pages and command-line tools each favour a different one. Converting between them is the whole job — and the ambiguity of the word "compression" is why the conversion is needed at all.
Where this tool stops
Arithmetic on the two sizes you enter. Bandwidth and time figures assume every transfer is the whole file and ignore HTTP overhead, caching and connection setup.
Explained in our guides
All guidesFrequently asked questions
Is "50% compression" a ratio or a saving?
Nobody can tell, which is the problem. A 2:1 ratio and a 50% saving describe the same file, but a "50% ratio" read literally would mean the output is half the size — a 2:1 ratio — while many people say it meaning 50% of the original was removed. Say <b>2:1</b> or <b>50% saved</b> and never the two words together.
What is bits per byte for?
It is how compression research states results, and it is the most comparable of the three. Uncompressed data is 8 bits per byte by definition; general-purpose compressors reach about 2 on English text, and the best experimental ones get near 1.
Why would compressed output be larger?
Because there was no redundancy to remove and the format added a header. Every general-purpose compressor grows some inputs — it is a mathematical necessity that no compressor can shrink every possible input, and already-compressed files are exactly the case where you meet it.
Are there any usage caps on the Compression Ratio Calculator?
There is no cost and no cap. The Compression Ratio Calculator is not a demo of a paid product, so nothing is held back or watermarked.
Is the Compression Ratio Calculator safe to use with private information?
No. The Compression Ratio Calculator runs entirely in your browser using JavaScript. Your input never reaches inputtesthub.com or any third party — open your browser's Network tab while you use it and you will see no request go out.
What formula does the Compression Ratio Calculator use?
It uses compression ratio = original ÷ compressed, space saving = 1 − compressed ÷ original, and bits per byte = 8 × compressed ÷ original. The full working is printed under the result, so you can follow every step rather than trusting a black box.
What do people use the Compression Ratio Calculator for most?
Typical uses: turning "3:1" into a percentage, or the reverse. Working out the monthly bandwidth a compression change saves. Comparing two compressors quoted in different units. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
Is there anything the Compression Ratio Calculator cannot do?
Arithmetic on the two sizes you enter. Bandwidth and time figures assume every transfer is the whole file and ignore HTTP overhead, caching and connection setup. Knowing where a tool stops being trustworthy matters more than the cases where it works.
What figures does the Compression Ratio Calculator work from?
Ratio is Original ÷ compressed, written as 3:1. Space saving is 1 − compressed ÷ original, written as 67%. Bits per byte is 8 means no compression; text usually lands near 2. These are printed on the page itself, so you do not have to take them on trust.
Can I rely on this for exact work?
The calculation runs in double precision and the result is shown to ten significant figures, so converting a value and converting it back returns the original. What is displayed is rounded for readability; what is copied is not.
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