<b>Short answer:</b><br><br><br><br>Just watch the damn video, it isn't any long and it's well made,(reply>), the video is the short answer<br>the single-sentence answer is because it’s impossible to calculate<br>the long answer is to get a degree in computer science and implement a progress bar yourself - why do you think so many mobile apps just show an endlessly spinning circle until it’s done? because that looks good and isn’t wrong,(reply>), i never thought i’d find myself siding with powerpoint