Ampère’s circuital law is used to calculate magnetic field at a point whenever there is a symmetry in the problem. This is similar to Gauss’s law in electrostatics. These are powerful methods whenever there is symmetry in the problem.
Ampère’s law: The line integral of magnetic field over a closed loop is μ0 times net current enclosed by the loop.
where Ienclosed is the net current linked by the closed loop C. Note that the line integral does not depend on the shape of the path or the position of the conductor with the magnetic field.