The torque (also moment) about an axis, due to a force, is a measure of the effectiveness of the force in producing rotation about that axis. The torque equation is:
  τ = rFsinθ
Where:
θ: The acute angle between the radial and force lines
r: The radial distance from the axis to the point of application of the force
F: The force

The torque on a looped coil, each carrying a current, in an external magnetic field is:
  τ = NIABsinθ
Where:
θ: The angle between the field lnes and a perpendicular to the plane of the coil
I: Current
A: Area of the coil
B: Magnetic field
N: Coil loops number