If you’ve looked at a neodymium magnet datasheet, you’ve seen grade names like N35, N52, 42SH, or 38UH. They can look like random codes, but they follow a simple system. Once you understand it, choosing the right magnet for your design becomes much easier.
The two parts of a grade name
Every NdFeB grade name has two parts:
- The number tells you how strong the magnet is.
- The letters tell you how well it resists heat and demagnetization.
For example, in 42SH, “42” describes the strength and “SH” describes the temperature resistance.
The number: magnetic strength
The number refers to the magnet’s maximum energy product, (BH)max, measured in MGOe (mega-gauss-oersteds). Put simply, it tells you how much magnetic energy the material can store.
- N35 has a (BH)max of about 33–36 MGOe
- N42 has about 40–43 MGOe
- N52 has about 49–53 MGOe
A higher number means a stronger magnet for the same size. An N52 magnet is roughly 50% stronger than an N35 magnet of identical dimensions, so you can often use a smaller N52 magnet to get the same force.
The letters: temperature resistance
The letters after the number show the magnet’s intrinsic coercivity (Hcj), its resistance to demagnetization. Higher coercivity lets the magnet work at higher temperatures without permanently losing strength.
| Suffix | Example | Hcj (min.) | Typical max working temperature |
|---|---|---|---|
| N (no suffix) | N42 | ≥12 kOe | 80°C |
| M | 45M | ≥14 kOe | 100°C |
| H | 42H | ≥17 kOe | 120°C |
| SH | 42SH | ≥20 kOe | 150°C |
| UH | 38UH | ≥25 kOe | 180°C |
| EH | 35EH | ≥30 kOe | 200°C |
| AH | 30AH | ≥35 kOe | 230°C |
Grades without a suffix are written with an “N” in front, such as N42. Grades with a suffix usually drop the N, such as 42SH instead of N42SH, although both styles are used in the industry.
Reading real examples
N52
The highest-strength standard grade, at about 49–53 MGOe. Its coercivity is relatively low, so it is rated for only about 60°C. Ideal for room-temperature applications where maximum force matters, such as holding magnets, consumer electronics, and compact devices. Not suitable for hot environments.
42SH
Strong, at about 40–43 MGOe, with super-high coercivity (Hcj ≥20 kOe). Rated for about 150°C, it’s a popular choice for industrial motors, inverter compressors, and automotive parts that run warm.
38UH
Slightly lower strength, at about 36–39 MGOe, but with ultra-high coercivity (Hcj ≥25 kOe). Rated for about 180°C, it suits servo motors, EV auxiliary motors, and other demanding thermal environments.
The trade-off: strength vs. heat resistance
At the top end, you generally can’t have both maximum strength and maximum heat resistance in the same grade. As coercivity increases, the highest available energy product usually decreases. That’s why an N52 is stronger than a 38UH at room temperature, while the 38UH keeps its strength far better as temperature rises.
The goal is to choose the strongest grade that can safely handle your maximum working temperature, with a reasonable safety margin.
Other numbers on the datasheet
Along with the grade name, datasheets list several key properties:
- Br (remanence): the magnetic flux density the magnet produces. Higher Br means a stronger field.
- Hcb (coercivity): the reverse field needed to reduce the magnet’s flux to zero.
- Hcj (intrinsic coercivity): the reverse field needed to fully demagnetize the material. This is the key value for heat resistance.
- (BH)max (maximum energy product): the overall measure of magnetic strength, and the number in the grade name.
Shape affects temperature limits too
Maximum working temperatures are guidelines, not guarantees. A magnet’s shape has a big effect. Thin, flat magnets demagnetize more easily than thick ones of the same grade, because they have a lower permeance coefficient. A thin N42 disc may start losing strength below 80°C, while a thick N42 cylinder may work above it.
When your design is close to a temperature limit, it’s safer to choose a higher coercivity grade or ask a magnet engineer to check your design.
How to choose the right grade
- Define your maximum working temperature, including peak temperatures, not just normal operation.
- Select a suffix that covers this temperature with a safety margin.
- Choose the highest number available in that suffix series that fits your budget.
- Consider the shape. Thin magnets may need a higher coercivity grade.
- Ask for samples and test them in your real working conditions.
Frequently asked questions
Is N52 always the best choice?
No. N52 is the strongest at room temperature, but it has low heat resistance. For anything above about 60°C, a grade like 45M, 42H, or 42SH will usually perform better.
What is the difference between 42H and 42SH?
Both have similar strength (about 40–43 MGOe), but 42SH has higher coercivity, so it can work at about 150°C instead of 120°C.
Do higher grades cost more?
Generally yes. Higher energy products and higher coercivity grades, especially UH, EH, and AH, require more advanced processing and often heavy rare earths, which increases cost.