What is my size for karate gi?

Hello I am enrolled in a karate class and I need a gi. However, no one in the school knows how to accurately size so I am confused on what size I should wear, and since the dojo is out of gis, I must order... anyway I am around 5'9 or 69 inches and I am around 200 lbs. Although I am not very tall and I am muscular due to years of athletics. As for Body type, I am not very bulky, or slim, the best description would be something like a decatheltes body. A balanced body.