How high can your cat or cats jump?

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I was minding my own business when out of the corner of my eye I saw one of my two six month old ginger tabbies flying through the air vertically! she was by the french windows and all of a sudden something caught her eye and up she went!, she has also taught her brother to do this and despite him being heavier also manages to reach an impressive height, so despite a lot of laughter my partner and I had about their new trick which is really highly amusing to watch, I was wondering how high other kitties can jump?! It must have been at least 5 or 6 foot but that is just an estimate!