Is a value used to describe the reduction in size of the data. For example if we start with a 1 Megabyte image and compress it to 128 Kilobytes, the compression ratio is 1,048,576 divided by 131,072 or 8. This represents a compression ratio of 8:1 meaning the compressed file is 1/8th the size of the original file. Typically the higher the compression ratio value, the worse the image looks. Compression ratio comparisons are only valid when using the same image format.