Choosing the right kite size can be a combersome for beginners. The correct size is a combination of your skills, board size, wind speed and weight.
I found this embedded excel sheet on James' Blog which gives you a rough idea of the size you need depending of the wind conditions and your weight.
It works great but sometimes I would like to quickly check on the go. So below is a quick dynamic chart I created which is mobile friendly (best viewed in landscape mode). I hope you find it useful.