Understanding the Gauss Measurement

We’re often asked if a magnet “has 10,000 Gauss” which is not a simple question to answer, since Gauss is a unit of magnetism that can apply to different measurements or magnet properties. A magnet doesn't have one specific measure of Gauss and the two common measurements expressed in Gauss are the Residual Flux Density, Br, and the Surface Field.

Residual Flux Density, Br, is the magnetic induction remaining in a saturated magnetic material after the magnetizing field has been removed. The Br value is measured under closed circuit conditions. A closed circuit condition exists wherein a magnetized permanent magnet is working by itself with no high permeability material, which is usually pure iron or low carbon steel. This means the air gap for the magnetic circuit is limitlessly large, and this number is a material property which is independent of the magnet shape. Grade N42 magnets have a Br of 13,200 Gauss, while N52 magnets can be as high as 14,800 Gauss.

The Surface Field is the strength of the magnetic field measured right at the surface of the magnet. It’s the field strength measured on a magnetometer’s sensor hard up against the surface of the magnet. The open circuit (not attached to any other ferrous object) surface Gauss value is the density of the magnetic field at any point on the surface of the magnet, and will depend on the magnet material, the shape of the magnet and how it’s used in a magnetic circuit.

For example, a 25mm diameter by 20mm thick N52 neodymium magnet, made from the strongest magnetic material commercially available will measure a maximum of 6,250 Gauss on the magnet’s surface.

Note; Magnets in open circuit conditions rarely exceed a value of 7,000 Gauss.

The actual measurement will depend on whether the magnet has any steel attached to it, how far away from the surface you make the measurement, and the size of the magnet (assuming that the measurement is being made at room temperature). For example, a 1" diameter N-48 Neo magnet that is 1/4"long, will measure approximately 2,800 Gauss 1/16" away from the surface, and 2,466 Gauss 1/8" away from the surface, and then considerably less as you move the magnet away from the surface.