Magnet Strength Input Form
Example Data Table
| Example | Grade | Shape | Dimensions | Gap | Use Case |
|---|---|---|---|---|---|
| Small sensor holder | N35 | Disc | 10 mm × 3 mm | 0.2 mm | Light alignment fixture |
| Cabinet catch | N42 | Block | 20 mm × 10 mm × 5 mm | 0.5 mm | Door holding estimate |
| Workshop mount | N52 | Disc | 25 mm × 10 mm | 0 mm | Direct pull comparison |
| Ring clamp | N48 | Ring | 30 mm OD, 10 mm ID, 8 mm | 1 mm | Fastener clearance study |
Formula Used
The calculator uses grade remanence, geometry, and gap distance to estimate axial field strength near the pole face. For non-round shapes, it converts the pole area into an effective radius.
Field estimate: B = Br / 2 × [((g + L) / √((g + L)² + r²)) - (g / √(g² + r²))] × circuit factor.
Pull force: F = B² × A / (2 × μ₀). The area is adjusted by contact efficiency and steel factor.
Flux: Φ = B × A. Magnetic moment: m = Br × volume / μ₀. Energy: E = BHmax × volume.
These formulas are simplified. Real results depend on steel thickness, plating, air gap, temperature, magnetization direction, surface finish, and test method.
How to Use This Calculator
- Select the nearest neodymium grade from the list.
- Choose disc, block, or ring shape.
- Enter the dimensions in millimeters.
- Add the air gap caused by paint, coating, plastic, or space.
- Enter temperature and correction settings when heat matters.
- Adjust contact efficiency and steel factor for real surfaces.
- Enter a required load to calculate a safety factor.
- Press calculate, then download CSV or PDF if needed.
Neodymium Magnet Strength Planning Guide
Neodymium magnet strength depends on grade, shape, size, air gap, and the steel target. A grade such as N35 or N52 gives an approximate remanence value. Higher remanence usually gives a stronger field, but geometry can change the final pull more than the grade label.
This calculator estimates useful engineering values from one set of inputs. It finds the effective pole area from the selected shape. It then uses magnet thickness, effective radius, and gap distance to estimate axial flux density. The result is not a certified laboratory reading. It is a planning value for comparing options, checking safety margins, and preparing first designs.
Air gap is very important. Even a thin layer of paint, plastic, glue, rust, or uneven steel can reduce holding force. Pull force also assumes a good magnetic path through flat steel. Thin steel, curved surfaces, low carbon content, or poor contact can reduce results. That is why the tool includes contact efficiency and a steel factor.
Temperature also matters. Standard neodymium grades lose field strength as temperature rises. The default coefficient reduces remanence by about 0.11 percent per degree Celsius above 20 degrees. High temperature grades need different coefficients and maximum ratings, so treat hot applications carefully.
The calculator gives pull force in newtons and kilogram force. It also estimates field strength in tesla and gauss, magnetic flux in webers, magnetic moment, and stored magnetic energy. These values help compare one disc, block, or ring against another.
For safety, use a large design margin. Magnets can chip, snap together, pinch skin, damage electronics, and affect medical implants. Do not rely on the computed pull force as the only support for heavy or critical loads. Test the real assembly with the exact steel, coating, orientation, temperature, and gap.
Use the example table to understand typical inputs. Then enter your own dimensions and grade. Start with a conservative contact efficiency. Increase it only when the magnet touches thick, clean, flat steel. For hanging or vibrating loads, add mechanical support. Magnetic force is strongest in direct pull. It is much weaker in shear unless friction or a retaining feature helps.
Record each trial so future material choices become easier, safer, and more consistent during product development and maintenance.
FAQs
1. What does magnet grade mean?
Magnet grade describes the maximum energy product of the material. Higher grades usually have stronger remanence. Shape, gap, and contact quality can still make a lower grade perform better in a real assembly.
2. Is the calculated pull force exact?
No. It is an estimate for planning and comparison. Certified pull force requires testing with the same magnet, steel plate, surface finish, temperature, and direction used in the final design.
3. Why does a small air gap reduce force?
Air has much higher magnetic reluctance than steel. Paint, plastic, dust, rust, or uneven contact increases the gap and weakens the magnetic circuit. Force may drop sharply even with a thin gap.
4. Can I use this for shear holding?
The result is mainly for direct pull. Shear holding depends on friction, surface texture, vibration, and any mechanical stop. Use a much larger safety factor for sliding or hanging loads.
5. Why is temperature included?
Neodymium magnets lose strength as temperature rises. Standard grades can also suffer permanent loss when overheated. Use the correct temperature grade for warm machines, motors, vehicles, or outdoor boxes.
6. What is contact efficiency?
Contact efficiency estimates how well the magnet face touches the target. Flat, clean, thick steel may use a higher value. Rough, painted, curved, or thin steel should use a lower value.
7. What does the steel return factor do?
It reduces the force for weak magnetic return paths. Thin steel, stainless steel, poor alloy choice, or small target plates can limit flux and lower the practical holding strength.
8. Should I add a safety factor?
Yes. Add a generous margin, especially for overhead, vibrating, moving, or safety related loads. Magnetic holding should not replace a mechanical fastener in critical applications.