Magnetic Dipole Moment Calculator

Calculate a current loop's magnetic moment, torque, and potential energy in a magnetic field.

Magnetic dipole calculation
Enter SI values for a coil and its external magnetic field.

About magnetic dipole moment

Magnetic dipole moment describes the strength and orientation of a magnetic source. For a flat current loop, its magnitude equals the electric current multiplied by the enclosed area. A coil with several identical turns contributes once per turn, so the practical expression is μ = NIA. The SI unit is ampere square metre (A·m²). The moment points perpendicular to the loop according to the right-hand rule: curl your fingers in the direction of conventional current and your thumb indicates the moment vector. When the coil is placed in an external magnetic field, its moment interacts with that field. The torque magnitude is τ = μB sin(θ), where θ is the angle between the moment vector and the magnetic field. Torque is greatest at 90 degrees and zero when the vectors are parallel or antiparallel. This tendency to rotate into alignment explains the operation of moving-coil meters, electric motors, magnetic compasses, and many laboratory demonstrations. The calculator converts the entered angle from degrees to radians before evaluating the trigonometric functions. The interaction also has potential energy U = -μB cos(θ). A parallel dipole has the lowest energy, an antiparallel dipole has the highest energy, and a perpendicular dipole has zero interaction energy under the chosen reference. The negative sign is physically meaningful: a freely rotating dipole tends toward the lower-energy aligned state. Current, area, turns, field strength, and angle must all describe the same coil at one instant for the three reported quantities to remain consistent. This model assumes a localized planar loop in a uniform magnetic field. It neglects wire thickness, field variation across the loop, magnetic core effects, and interactions between turns. Use the result for ideal coils, introductory electromagnetism, and first-order engineering estimates. Real solenoids, ferromagnetic cores, or spatially varying fields may require integration or measured material properties. Keep all inputs in the displayed SI units; convert square centimetres to square metres and milliteslas to teslas before calculating. The tool preserves scientific notation for very small or very large results, making both classroom examples and compact electromagnetic devices easy to compare.

Magnetic dipole examples

These ideal current-loop examples use SI units.

InputsResultsInterpretation
I = 2 A, A = 0.5 m², N = 1, B = 0.2 T, θ = 90°μ = 1 A·m², τ = 0.2 N·m, U = 0 JA perpendicular loop experiences maximum torque.
I = 3 A, A = 0.02 m², N = 50, B = 0.4 T, θ = 0°μ = 3 A·m², τ = 0 N·m, U = -1.2 JAn aligned coil is at minimum potential energy.
I = 0.5 A, A = 0.01 m², N = 100, B = 0.1 T, θ = 180°μ = 0.5 A·m², τ = 0 N·m, U = 0.05 JAn antiparallel coil is an unstable equilibrium.

How to use the calculator

  1. Enter the current through the loop in amperes.
  2. Enter the area of one turn in square metres and the number of turns.
  3. Provide the external magnetic field in teslas and the angle to the moment vector.
  4. Select Calculate dipole moment to obtain moment, torque, and potential energy.

Frequently asked questions

What is magnetic dipole moment?

Magnetic dipole moment is a vector measure of a magnetic source's strength and orientation. For an ideal coil, its magnitude is the number of turns times current times loop area.

Why does the number of turns multiply the moment?

Each identical turn creates a moment in the same direction. Their contributions add, so a tightly wound N-turn coil has N times the moment of one turn under the ideal model.

Which angle should I enter?

Enter the angle between the magnetic moment vector and the external magnetic field. It is not generally the angle between the plane of the loop and the field, because the moment is normal to that plane.

When is magnetic torque greatest?

The torque reaches its greatest magnitude when the moment and field are perpendicular at 90 degrees. It becomes zero at 0 or 180 degrees, although the antiparallel state is unstable.

Can I use centimetres and milliteslas?

Convert them before entering values because this calculator expects SI units. Divide square centimetres by 10,000 for square metres and divide milliteslas by 1,000 for teslas.