Compressieratio

Compressieratio is a dimensionless measure used to describe how much a quantity is reduced by a compression process. The exact meaning depends on the domain, but it generally expresses the ratio of the original quantity to its compressed form.

In data compression, the ratio is typically defined as the size of the original data divided by the size of the compressed data. A 10:1 ratio means the compressed file is one tenth the size of the original. Ratios can be higher for highly repetitive data and lower for already compact content. The methods used to achieve compression are categorized as lossless (where all original information can be recovered, as in ZIP or PNG) or lossy (where some information is discarded, as in JPEG or MP3). In practice, the compression ratio depends on the data characteristics and the algorithm.

In internal combustion engines, the compression ratio refers to the ratio of the cylinder volume when the piston is at bottom dead center to the volume when it is at top dead center. Higher ratios improve thermal efficiency but increase the risk of pre-ignition and knock. Gasoline engines typically run around 8:1 to 12:1, while diesel engines operate with higher ratios, approximately 14:1 to 25:1.

In other contexts, compression ratio can apply to images, audio, and general data, with convention sometimes varying. Some sources use the reciprocal as the compression factor. Because interpretation depends on context, it is important to specify the definition used when reporting a compressieratio.