Magnet Surface Field, Units, and Influencing Factors

"How many Gauss is this magnet?" is one of the most common customer questions. But surface magnetic field is affected by many factors, and it is not the same thing as "how much weight it can hold." This article clarifies the basic concepts and common misconceptions about magnetic field.

Units of magnetic field: Gauss and Tesla

A magnet's field strength (magnetic flux density) is often expressed in Gauss (G) or Tesla (T). The conversion between them is simple:

The surface field of a typical NdFeB magnet ranges from a few hundred to just over six thousand Gauss, depending on grade, shape, and measurement position.

Br remanence: the material's inherent limit

Remanence Br is a property of the magnet material itself, determining the inherent upper limit of magnetic force it can achieve. The higher the grade (for example, N52 versus N35), the higher the Br and the stronger the force. But Br is the "material's potential"; the surface field actually measured is further affected by shape and measurement conditions.

Factors affecting surface magnetic field

• Magnet grade: N35–N54; the higher the grade, the stronger the field.
• Shape ratio: For the same material, the larger the height/diameter (thickness ratio), the higher the surface field. A thin disc has a noticeably lower field than a thick cylinder of the same diameter.
• Measurement distance: The field falls off rapidly with distance; even a small gap from the surface drops the value noticeably. So a "Gauss" figure must always state the measurement position.
• Magnetic circuit: Pairing with an iron yoke to guide and concentrate the magnetic path can greatly increase the single-side field and holding force—this is why a magnetic cup assembly holds far more than a bare magnet.

Surface field ≠ pull force

Many people assume "higher Gauss means it holds more weight," but the two cannot be equated directly. Pull force (holding force), besides being related to the field, is also affected by contact area, the material and thickness of the object being attracted, and the gap. A large-area magnet does not necessarily have the highest Gauss, but its large contact area may give greater total holding force. To assess how much weight it can hold, look at pull force rather than Gauss alone.