Every week we receive RFQs that simply say “N52 magnets, 10,000 pcs, best price.” And every week we reply with two questions instead of a quote: what is your maximum working temperature, and how thin is the magnet? The reason is that the neodymium magnet grades system promises far less than most buyers assume: on a hot or thin part, an expensive high grade can be beaten by a cheaper one with the right temperature suffix.
This is the reference we use internally when a grade discussion starts. It decodes the whole neodymium magnet grades system — the strength number (N35 to N54) and the temperature suffix (M, H, SH, UH, EH, AH) — with the actual values behind each code, and the selection logic we apply when customers ask us to pick for them. If you want to compare two specific grades right now, our grade comparison tool does the side-by-side math in a few clicks.
If you are brand new to the material itself, start with what NdFeB magnets are, then come back here — this article assumes you know the basics.
What Neodymium Magnet Grades Actually Encode
A grade code has two parts, and they describe two independent properties:
N42SH = N (neodymium) + 42 (strength) + SH (temperature class)
- The number (35–54) tracks the maximum energy product (BH)max in Mega-Gauss-Oersteds (MGOe). Bigger number, more magnetic energy per unit volume — in practice, a stronger magnet of the same shape.
- The letter suffix (M, H, SH, UH, EH, AH) is the intrinsic coercivity (HcJ) class — how hard the magnet fights permanent demagnetization, which is what heat attacks first. No suffix means the base class: safe up to about 80 °C.
Two consequences follow immediately, and they trip up a lot of first-time buyers:
- “N52 is just a stronger N42” is only true at room temperature. An unsuffixed N52 sitting at 90 °C can lose flux permanently, while a plain N35SH — nominally much “weaker” — shrugs it off.
- The grade says nothing about magnetization direction, coating, or tolerance. Those are separate specifications, and leaving them out of an RFQ is how mismatched shipments happen.
The Strength Number: N35 to N54
All values are room-temperature (20 °C) typical ranges for sintered NdFeB, in line with GB/T 13560 and the major manufacturer datasheets. Numbers vary slightly between producers — always confirm against the supplier’s test report, not the datasheet of a random distributor.
| Grade | Remanence Br (kGs) | (BH)max (MGOe) | Min. HcJ (kOe) | Max. operating temp* |
| N35 | 11.7–12.1 | 33–36 | ≥ 12 | 80 °C / 176 °F |
| N38 | 12.1–12.5 | 36–39 | ≥ 12 | 80 °C / 176 °F |
| N40 | 12.5–12.8 | 38–41 | ≥ 12 | 80 °C / 176 °F |
| N42 | 12.8–13.2 | 40–43 | ≥ 12 | 80 °C / 176 °F |
| N45 | 13.2–13.6 | 43–46 | ≥ 12 | 80 °C / 176 °F |
| N48 | 13.7–14.1 | 46–49 | ≥ 12 | 80 °C / 176 °F |
| N50 | 14.0–14.5 | 48–51 | ≥ 12 | 80 °C / 176 °F |
| N52 | 14.3–14.8 | 50–53 | ≥ 12 | 80 °C / 176 °F |
| N54 | 14.5–15.0 | 52–55 | ≥ 11 | 80 °C / 176 °F |
* For the standard (no-suffix) class. The operating-temperature story changes completely with a suffix — that is the next table, and for most engineering decisions it matters more than this one.
Notice how narrow the remanence range really is: from the “entry level” N35 to the strongest production grade N54, remanence moves by roughly 25%. The difference shows up mostly in energy product, and it costs money: the per-MGOe price climbs steeply above N45. For a part that lives at room temperature, N42 or N45 is very often the sweet spot — you pay a premium for N52+ that buys you a smaller magnet, and “smaller” is only worth money if volume is genuinely constrained in your design.
The Temperature Suffix: M, H, SH, UH, EH, AH
Heat is the natural enemy of NdFeB. As temperature rises toward the Curie point (about 310–370 °C depending on composition), coercivity falls — and if it falls far enough, domains begin to flip and the magnet loses flux permanently, even after cooling down. The suffix classifies how much margin a grade has against that mechanism:
| Suffix | Min. HcJ (kOe) | Max. operating temp* | Heavy rare earth (Dy/Tb) in composition** |
| (none) | ≥ 12 | 80 °C / 176 °F | None |
| M | ≥ 14 | 100 °C / 212 °F | None to trace |
| H | ≥ 17 | 120 °C / 248 °F | None to trace |
| SH | ≥ 20 | 150 °C / 302 °F | Usually none — Dy/Tb-free is standard |
| UH | ≥ 25 | 180 °C / 356 °F | Typically Dy additions |
| EH | ≥ 30 | 200 °C / 392 °F | Dy, sometimes Dy + Tb |
| AH (also written TH) | ≥ 33 | 230 °C / 446 °F | Dy + Tb |
* Typical values for a conventional disc or block with a sensible length-to-diameter ratio, defined as the temperature at which irreversible flux loss stays within about 5%. Thin or short magnets demagnetize earlier — see the geometry section below.
** Rule of thumb from our own production experience; exact metallurgy is a per-supplier decision. This column matters more than it looks — see the export-control section.
Two things to read out of this table:
You trade peak strength for heat resistance. The suffix ladder caps how strong the top grades can go: the strongest common UH grade is N45UH (43–46 MGOe) and the strongest EH grade is N42EH (40–43 MGOe) — both well below N54’s 52–55. There is no “N52EH” in any practical sense. If your application needs both high temperature and high energy product, you are shopping at the intersection, and the honest options get expensive (or you switch chemistry — more on that below).
The suffix is bought with heavy rare earths. Raising HcJ from 12 to 30+ kOe is done mostly by adding dysprosium (and terbium at the top of the ladder) into the grain boundaries. That ingredient reality is invisible in the magnet’s performance but very visible in its price, its supply chain — and, since 2025, its paperwork.
How to Read a Full Grade: N42SH
Take the most specified grade we ship, N42SH, and decode it completely:
- N — sintered neodymium-iron-boron.
- 42 — BHmax in the 40–43 MGOe band; remanence 12.8–13.2 kGs. Strong, but not the exotic top of the range.
- SH — HcJ at least 20 kOe; safe to about 150 °C with conventional geometry.
What N42SH does not tell you — and what must be on the drawing instead: magnetization direction (axial, radial, diametric, multipole), coating (NiCuNi, zinc, epoxy…), dimensional tolerances, and whether the 150 °C rating is continuous or includes excursions. A grade plus a drawing is a specification; a grade alone is a wish.
The Max Operating Temperature Is Not a Guarantee
The single most common misunderstanding we deal with: a buyer reads “80 °C” from the table, their part runs at 75 °C, and they assume they are safe. Three things can still bite:
Geometry. Those table values assume a magnet with a reasonable length-to-diameter ratio (roughly L/D ≥ 0.5) in free space. A thin disc or a short ring has a low permeance coefficient — the demagnetizing field from its own poles is relatively stronger — and can start losing flux irreversibly well below the grade’s rated temperature. This is why the same grade behaves differently in a fat block and in a 1 mm-thick washer.
Load line and opposing fields. In motors and actuators, armature reaction and other nearby magnets add demagnetizing fields on top of temperature. A grade chosen from a table alone, without the circuit’s load line, is a guess.
Self-heating. In dynamic applications the magnet’s environment is hotter than the ambient you measured. Eddy currents in conductive tooling, coil proximity, friction — the operating point to check is the magnet’s actual temperature, not the room’s.
We cover the thermal side in depth in our high-temperature NdFeB selection guide, including the grade-vs-temperature worked examples. When in doubt, send us the geometry and the environment instead of the grade — specifying from first principles takes a day and prevents a very expensive redesign.
Stronger Is Not Better: How We Actually Pick a Grade
Our internal order of questions, which is also the order we recommend buyers think in:
1. Working temperature first. It eliminates half the table immediately. A part living at 160 °C needs SH-or-better no matter what; below 70 °C, the entire ladder is open.
2. Then the strength class, not the strength maximum. Ask what flux density the circuit actually needs at the working point. Often a cheaper grade in a slightly larger volume beats a premium grade — magnet material is priced per MGOe, and geometry is usually the cheaper currency.
3. Then volume constraints. Only if the envelope is truly fixed does the top of the range (N50–N54) earn its premium.
4. Then the supply-chain realities — which in 2025 and 2026 include export controls, covered next.
| Typical requirement | Grades we normally quote | Why |
| Consumer products, stationery, holders | N35–N38 | Cost-driven; no thermal stress |
| General industrial fixtures, sensors | N42 | The value sweet spot |
| Compact high-force parts (separators, audio, couplings) | N45–N52 | Volume-constrained designs |
| Automotive under-hood sensors, pumps (≈150 °C) | N35SH–N45SH | Dy/Tb-free achievable |
| BLDC and EV traction motor rotors (≈180 °C) | N35UH–N42UH | Standard motor territory |
| High-temperature motors, actuators (≈200 °C) | N35EH–N40EH | Dy-bearing; check licensing |
| Extreme thermal environments (≈230 °C) | N30AH–N38AH | Niche; often SmCo wins instead |
One boundary worth knowing: above roughly 250–300 °C, stop shopping in the NdFeB aisle. Samarium-cobolt takes over there — lower Br but a much higher Curie temperature and superb corrosion behavior. We produce both, and our SmCo magnets page covers the crossover zone; the honest summary is that forcing NdFeB past its thermal design window costs more than switching material.
The Compliance Dimension: Grades, Dysprosium and Export Licensing
Since April 2025, the neodymium magnet grades ladder has had a second meaning that no grades chart mentioned before then: it is also a licensing ladder. China’s export controls on magnet technologies (Ministry of Commerce Announcement No. 18) key off heavy rare earth content — and heavy rare earths are exactly what the higher temperature suffixes are made of.
The practical map, from our production floor:
- N through SH can be produced without any dysprosium or terbium. In our experience these grades ship on the normal timetable with no license involved.
- UH, EH and AH normally rely on Dy/Tb additions to reach their coercivity class, which puts them on the controlled route — where licensing has taken about four months in our 2025–2026 experience.
If you want the full decision procedure — including the 0.1% content benchmark customs applies in enforcement and the four-step classification test — read does your neodymium magnet need an export license? and the Announcement No. 18 explainer behind it.
This is also why we invested heavily in HRE-free high-coercivity grades: grain-boundary diffusion technology reaches SH-class coercivity — and in specific designs beyond — without dysprosium or terbium, keeping parts on the fast route while holding the thermal rating. If your schedule cannot carry a four-month license, that is the first lever to pull; the engineering details are in our HRE-free NdFeB guide.
The buyer’s takeaway: a grade choice made on magnetics alone can add four months to your delivery. Ask your supplier two questions early — “what is the Dy/Tb content of this grade as you produce it?” and “does this part trigger licensing?” — before the design freezes.
Four Mistakes We See in Incoming RFQs
Defaulting to N52 for a room-temperature part. Unless the envelope is fixed and small, N42 or N45 delivers the same field for meaningfully less money. The premium grades earn their place only where volume is the binding constraint.
Trusting the temperature number without the geometry. The tables assume conventional shapes. Thin discs, short rings and washer geometries derate hard; check the load line before you check the price.
Specifying a grade but not a magnetization direction. “N42, 20 × 10 × 5 mm” can be magnetized three different ways and be three different products. The grade and the drawing must travel together.
Choosing UH or above without checking the compliance clock. A technically perfect grade that adds a four-month license to every shipment is rarely the right engineering answer — the HRE-free route or a one-step-down grade with better geometry often wins on total cost and schedule.
FAQ
What is the strongest neodymium magnet grade? N54 is the strongest production grade at room temperature (BHmax 52–55 MGOe, Br up to about 15.0 kGs), with N52 close behind and usually easier to source. The theoretical ceiling for NdFeB is around 64 MGOe. Remember the catch: unsuffixed grades hold those numbers only near room temperature.
Which grade should I use at 150 °C? SH class is designed for it — N42SH is the workhorse choice, with N35SH–N45SH all viable depending on the strength you need. At 180 °C move to UH, at 200 °C to EH, at 230 °C to AH. Beyond that, look at samarium-cobalt. And always re-check with your real geometry, because thin parts derate earlier than the table suggests.
Is N52 twice as strong as N35? No — and this misconception causes budget waste. N52’s energy product (50–53 MGOe) is about 45% higher than N35’s (33–36 MGOe), and pull force scales less than energy product does once geometry is fixed. If you need more force, a geometry change or a one-or-two-step grade bump is usually cheaper than jumping to the top of the range. Our comparison tool shows the two grades side by side, and the unit converter handles the kGs / kOe / MGOe / SI conversions when you are cross-checking datasheets.
What do the letters after the number mean, in one sentence? They are the intrinsic-coercivity class — how much demagnetization margin the grade has — which translates into a maximum operating temperature: M 100 °C, H 120 °C, SH 150 °C, UH 180 °C, EH 200 °C, AH 230 °C, for conventional shapes.
Why did my magnet arrive weaker than the datasheet value? Most often one of three things: the part is running hotter than its rating (partial, permanent flux loss), the geometry derates the working point below the datasheet assumptions, or the measurement method differs from the supplier’s (a fluxmeter reading on a specific fixture is not the same number as BH-curve data). A proper incoming inspection compares like with like — test report from the supplier, same fixture on your side.
The Short Version
Pick the temperature suffix from your real operating temperature and geometry, then buy the lowest strength number that meets the circuit’s flux requirement — and in the current environment, ask about heavy rare earth content before you freeze the design, because the letter after the number now determines not just the performance but the paperwork.
If you want a second pair of eyes on a grade selection, send us the drawing, the working temperature and the environment — we quote from first principles, and we will tell you honestly when a cheaper grade or an HRE-free route does the job. Start at our NdFeB magnets page or contact us directly.
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