torx was originally made for japanese cars, and so in order to understand the measurement you need to know some japanese culture
the size of a torx bit is the equivalent of the height of the amount of bowls of rice after a sumo wrestler sits on it
a T5 bit then, (meausured across the tips of two opposing point of the star) is just as wide as 5 bowls of rice would be tall after a sumo wrestler sat on it
a T25 bit is as far across as 25 bowls of rice would be tall after the sumo wrestler sits on it
(this does have to be a championship weight sumo wrestler, or it will throw off the conversion)