What is a good compression ratio?
A good compression ratio depends on the data type and the acceptable quality loss; there is no universal number that fits every situation.
Context and definitions
Compression ratios express how much smaller a file becomes after encoding. They are usually reported as a ratio of the compressed size to the original, for example 10:1 means the output is one-tenth the input. The choice between lossless and lossy methods is central: lossless preserves every bit, while lossy sacrifices some information for smaller files and faster transmission.
Lossless vs lossy
Lossless compression is essential when exact reproduction is required, such as source code, sensitive documents, or archival data. Lossy compression is common for media where a small, deliberate loss of fidelity is acceptable in exchange for much smaller files or lower bandwidth usage—images, audio, and video are typical examples. The key question is whether the application can tolerate minor quality changes in exchange for big size or speed gains.
Common domains and typical ranges
Different data types yield very different practical ratios. The following ranges are approximate and depend on content, quality targets, and encoding settings. Use them as benchmarks rather than guarantees.
- Text and software source code (lossless): typically 2:1 to 3:1, with highly repetitive data occasionally reaching 5:1.
- Images:
- Photographs and complex imagery (lossy): commonly 8:1 to 20:1 depending on the desired quality.
- Lossless images (PNG, WebP lossless): generally 1:1 to 3:1, depending on content specifics.
- Audio:
- Compressed formats (MP3, AAC, Ogg Vorbis): roughly 6:1 to 12:1 for good perceptual quality at typical bitrates.
- Lossless audio (FLAC, ALAC): 1:1 (no size reduction beyond data content); containers/metadata can affect total size.
- Video (lossy codecs like H.264/HEVC/AV1): often 20:1 to 50:1 or more, highly dependent on motion, resolution, and target quality.
- Data archives and databases (textual or structured data): 2:1 to 6:1 with modern compressors (e.g., Zstandard, LZMA); highly repetitive data can push beyond these bounds.
In practice, the best ratio is the one that meets storage, bandwidth, and performance constraints without unacceptable degradation in usefulness or experience. Always test with representative data to confirm.
How to decide what constitutes a "good" ratio
A practical, repeatable approach helps determine a suitable compression ratio for a given use case. The steps below guide decision-making across typical scenarios.
- Define the goal: quantify how much space or bandwidth you must save and what latency or CPU cost you can tolerate.
- Assess acceptable quality loss: specify metrics or user experience thresholds (e.g., acceptable PSNR/SSIM for images, MOS for audio/video).
- Test with representative data: run multiple codecs and settings on real workloads to observe actual ratios and quality.
- Consider delivery constraints: streaming, offline storage, or on-device decoding may favor different codecs and presets.
- Benchmark and iterate: compare end-to-end performance, not just file size, and adjust accordingly.
Bottom line: validate through real-world testing and measure the impact on users, storage, and network resources. A seemingly large ratio is not helpful if quality suffers or performance tanks.
Practical tips for achieving a good ratio
To optimize compression while keeping quality within acceptable bounds, consider these guidance points:
- Choose modern codecs and tuned presets appropriate for your data type (e.g., AV1/WebP for video/images, HEVC for high-end video, FLAC for archival audio).
- Prefer lossless compression when fidelity is non-negotiable; resort to lossy compression only when the perceived quality remains acceptable.
- Use multi-pass or rate-distortion optimized encoding to improve the trade-off between size and quality.
- Minimize metadata and container overhead, which can inflate apparent size without affecting essential data.
- Adapt bitrate or quality settings to the delivery channel (e.g., adaptive streaming for varying network conditions).
- Document and standardize the acceptable quality thresholds so downstream systems can maintain consistency.
When applied thoughtfully, these practices help you achieve meaningful reductions without sacrificing the user experience or data integrity.
Summary
The notion of a single “good” compression ratio is context-specific. Text and data tend to compress modestly up to about 2:1–5:1 lossless, images and video can achieve much higher ratios with lossy methods (depending on quality targets), and lossless media like FLAC or PNG have limited room to shrink. The most reliable path is to define quality requirements, test with real data, and balance size savings against performance and fidelity. Modern codecs and careful encoding choices enable meaningful gains across domains while preserving acceptable user experience.
What octane is best for 12 to 1 compression?
110, 100 minimum. I would use 100 on my 12:5:1 and when I was going run it hard or use the bottle I would use 110.
What is a good engine compression ratio?
Compression ratios are often between 14:1 and 23:1 for direct injection diesel engines, and between 18:1 and 23:1 for indirect injection diesel engines. At the lower end of 14:1, NOx emissions are reduced at a cost of more difficult cold-start.
What psi is 10 to 1 compression?
about 150 to 200 psi
A rough estimate of cylinder pressure is 15 to 20 times the compression ratio. So 10:1 should produce about 150 to 200 psi.
Is a higher compression ratio better?
A higher compression ratio is generally better for an engine because it increases thermal efficiency, leading to more horsepower and better fuel economy. However, there are limits; a ratio that is too high can cause pre-ignition (knocking) and may require higher-octane fuel. For some engines, especially those with forced induction, lower compression can be a necessary trade-off to prevent detonation.
Benefits of a higher compression ratio
- Higher thermal efficiency: A higher ratio allows the engine to extract more mechanical energy from the air-fuel mixture, converting more heat into power.
- More horsepower: This increased efficiency directly translates to more horsepower for a given engine displacement.
- Improved fuel economy: By more efficiently using the energy in the fuel, a higher compression ratio can lead to better mileage.
Drawbacks and limitations
- Fuel requirement: As compression increases, so does the need for higher-octane fuel to prevent pre-ignition.
- Risk of detonation: If the compression ratio is too high for the fuel being used, the fuel can self-ignite prematurely, causing engine knock or pinging.
- Engine stress: Excessively high compression can put immense stress on engine components, potentially leading to failure.
For specific engine types
- Naturally aspirated engines: A high compression ratio is generally a priority for maximizing performance in a naturally aspirated engine.
- Forced induction engines: In engines with turbochargers or superchargers, a lower compression ratio is often necessary to prevent detonation at high boost levels. In these cases, the gains from the forced induction outweigh the efficiency loss from the lower compression ratio.
