I would like if someone could clarify this issue for me: When dealing with a current $I$ running in a loop with radius $R$ and looking for the magnetic field in the middle of the loop. By using Ampere's law, i know that the current $I$ runs through a loop with the same radius $R$ ,we get that: $$\int(B*dl) = \mu I $$
$$B= \mu I/2\pi R $$
and when using BIO-SAVART we get that $$dl*r = |dl||r|sin90$$ and therefore i get that: $$B = \mu I/2R$$
Which is not the same result as with ampere's law. I obviously miss something, maybe i can't use Ampere's law? Anyway, if someone could help me out here I would really appreciate it. Thanks.