What is the maximum compression ratio of gzip?

Update 2020-02-06: As mentioned in the comments, I have been unable to reproduce the original result with gzip. Working on the assumption that I accidentally used a different compression format in that original quick test I've repeated with gzip and updated the figures below accordingly. This new result agrees with the theoretical maximum compression stated in other answers/comments. It very much depends on the data being compressed. A quick test with a 1Gb file full of zeros using a standard v…