If two factories measure the same magnet and get different numbers, which one is right? That is exactly the problem testing standards are designed to solve. They define how to measure, what equipment to use and how to report results, so a grade number means the same thing in China, Europe or the United States.
The main standards families
The three families you will meet most often:
- GB/T — the Chinese national standards. GB/T 13560 covers sintered NdFeB, and most Chinese magnet certificates are written against it.
- IEC — international standards used across Europe and much of the world. IEC 60404 is the key document for magnetic materials testing.
- ASTM / MMPA — American standards, common when selling into North America.
The three families agree on the core idea: measure the same properties with similar methods. Small differences in equipment and procedure remain, so numbers from different labs can vary slightly.
What gets measured
Standard testing covers the four key parameters: Br (remanence), Hcb and Hcj (coercivity) and (BH)max (energy product). Measurements are made on closed-circuit equipment or with pulse magnetizers that fully magnetize the sample first. Open-circuit measurements give different, lower numbers, so always check which method the report describes.
What to ask your supplier
Most manufacturers certify to one standard — usually GB/T in China. Before comparing quotes, ask which standard the test report follows and whether the values were measured on the actual batch. A certificate is only useful if you know what it means, so read the method notes as carefully as the numbers.
Read on: GB/T standards guide → · incoming inspection →