What're the chances i will go through a growth spurt soon if i'm 18?

Stage of puberty : Most boys and girls are done growing by 18. However, some may have a delay in pubertal development which could lead to a growth spurt later in adolescence. It is difficult to answer without at least and x-ray of your left hand which would help to identify if you still have open growth plates. If you have concerns regarding delayed puberty or a slow growth rate, please discuss this with your doc.

Growth: Growth at 18 is rare in either boys or girls. If one had very delayed puberty there is a slight chance. The only way to find out if it's possible is a "bone age" x-ray. This can determine whether the growth plates of the bones have fused closed.