Napoleon was not short, it is a combination of two things. First there is the famous cartoons of the time which shows him as short to the rest, so it's come down through the years that he was short when in reality, he was 5'7". This is the next problem, according to Imperial units, he is 5'7", but with the French inch he was 5'2" so without the proper conversion, he seems short. Further, he kept his Imperial Guard with him at all times, made up of some of the tallest men in France, so his Guard would tower over him yet, making him shorter than those around him.

All in all, he wasn't short, he was a little tall for the age.

He was actually common size for a french man of that time period, the rumor about his size was spread by his enemies.