Magnetic Pull Force: What Determines a Magnet’s Strength?

Not all magnets are created equal. Two magnets of the same size can have drastically different holding powers depending on various factors. In this post, we’ll explore what determines a magnet’s pull force and how you can choose the right one for your application.

1. Magnet Material: Neodymium vs. Ferrite vs. Alnico

The most important factor is the magnetic material. Neodymium (NdFeB) magnets are the strongest permanent magnets commercially available. Ferrite or Alnico magnets of the same size are significantly weaker.

Example:
A 10 mm neodymium disc can hold over 2 kg – while a ferrite magnet of the same size might only manage 0.3 kg.

2. Size and Volume

Pull force increases with the surface area and volume of the magnet. A larger magnet has more magnetic field lines and a greater area to transmit them into the ferromagnetic object it’s attached to.

3. Shape and Construction

Shape matters. A disc magnet, a cube, or a pot magnet can behave differently. Pot magnets, in particular, are designed to concentrate the magnetic field on one side, significantly boosting their effective pull force.

4. Air Gap and Surface Contact

Even a tiny air gap between magnet and metal – caused by paint, rust, or uneven surfaces – can drastically reduce pull force. Smooth, clean contact surfaces allow for the strongest possible hold.

5. Temperature

Neodymium magnets begin to lose strength above 80 °C (176 °F). Some high-temperature grades tolerate more, but others weaken quickly in hot environments. Extremely cold temperatures (below −20 °C / −4 °F) can also slightly affect performance.

6. Direction of Pull

Magnets are strongest when pulling straight away from a surface (axial pull). Sideways forces (shear force) are much weaker, so magnets can slide off if the load isn’t properly aligned.

7. Magnet Grade

Neodymium magnets come in grades like N35, N45, N52. A higher grade means a stronger magnetic field for the same size – but typically with reduced heat resistance.

Conclusion: Magnet Strength Is a Balance of Factors

When evaluating a magnet’s holding power, consider material, shape, contact surface, temperature, and direction of use. The strongest magnet isn’t always the biggest – sometimes, choosing the right type and design is the key.

🧲 Tip: On yourmagnets.net, you can filter magnets by pull force range (e.g. 4–6 kg or over 20 kg) to find the perfect match for your needs.