Help me choose the right size bike! please?

[kneekahloo]

Im 15 years old and want to get a new fixed gear bike. I only have enough money for a Mercier Kilo TT, which im fine with. Im about 5'8" and i dont know whether to get a 53cm or a 55cm. I dont know how to find my inseam or my stand-over height. help me?

 

[peter]

It is good to select the MTB bike as a boy
freely city bike as a girl.