Magnetic Moment Calculator
magnetic moment of an NdFeB magnet in A·m²
The magnetic moment describes how strong a source of field a given magnet is as a whole. The result is expressed in ampere square metres (A·m²) and is derived from the remanence of the material and the volume of the body. Pick a shape, enter the dimensions in millimetres and select the magnet grade.
| Magnetic moment: | — |
|---|---|
| Volume: | — |
| Volume: | — |
| Remanence Br used: | — |
mid-range value for the selected grade
Magnetic moment - what this number means and why it matters
What the magnetic moment is
The magnetic moment is a single number that describes an entire magnet as a source of field. It does not tell you how firmly the magnet will stick to a particular steel plate - it tells you how strong a dipole the magnet is on its own. That makes it useful for comparing magnets with each other regardless of what they will be attached to, and for feeding into calculations of magnetic circuits, torque in an external field or the interaction between two magnets at a distance. The value grows with the volume of the body and with the grade of the material - two magnets of identical volume but different grades will have different moments.
What this calculator does not do
This calculator does not predict pull force. An ampere square metre is not a kilogram and one cannot be converted into the other without knowing the contact conditions. Breakaway force depends on the thickness and grade of the attracted steel, on the air gap, on surface roughness and on the direction in which the force acts - none of these appear in the formula for magnetic moment. If you are looking for holding force expressed in kilograms, use the magnet pull force calculator. Treating the magnetic moment as a holding force leads to selecting a magnet with entirely unsuitable parameters.
Why we use the mid-range Br value
A magnet grade such as N42 does not denote a single remanence value but a range - here from 12.9 to 13.2 kGs. The manufacturer guarantees that the finished magnet will fall within that range, but does not declare where inside it. For the calculation we take the middle of the range, because it gives the result closest to an average production batch. A result based on the upper limit would be a few percent higher, one based on the lower limit a few percent lower. That is why we show the Br value actually used alongside the result - it makes clear where any difference comes from when comparing against a calculation performed with a different remanence.
See also
- neodymium magnet pull force calculator - breakaway force in kilograms
- magnetic force and flux density calculator - flux density at a distance from the surface
- SI unit calculator - conversion of magnetic units