Permanent magnets are graded by the maximum energy the magnet produces. Typically, the higher the magnet grade, the higher the corresponding strength of the magnet.
Magnetic strength is most often measured in two ways, grade and pull strength. Raw magnetic materials are commonly measured by grade, and magnetic assemblies by pull strength. For the purposes here, the focus will remain on grades. For information about pull strength, refer to our post Measuring Pull Strength.
To determine the strength of a permanent magnet, we measure Gauss, which is the amount of attractive force the magnet possesses. Additionally, we measure Oersteds, which is the permanence of that force. Because both traits are desirable in magnets, multiplying Gauss and Oersteds determines the Max Energy Product referred to as MGOe (Mega Gauss Oersteds) – which is the number used to grade the magnet.
Because temperature plays a large role in the long-term performance of a neodymium magnet, there may also be a letter after the grade of neodymium magnets. This is a standard rating for progressively higher temperatures for neodymium 35 (M, H, SH, UH, EH, or AH). For standard neodymium, no letter simply indicates a maximum operating temperature, which is 80⁰ C.
Currently, the strongest grade of magnetic material is neodymium, however each type of magnetic material has its advantages.
Common Magnetic Material by Grade Range:
Choosing a magnet may not be as simple as selecting the highest grade available. The application is critical in the specification process. In most cases, the same strength can be achieved by utilizing a slightly larger magnet, with a lower grade and at a cost savings. Heat, moisture, torque, and chemical exposure can all affect the strength and size of the magnet required for a project.
We always recommend consulting with our magnetic specialists to help select the best magnet for the application.