How strong is a neodymium magnet?
Short answer: neodymium magnets are the strongest permanent magnets you can buy: about 5 to 10 times stronger than an ordinary (ferrite) magnet of the same size. A Ø10 x 3 mm disc magnet holds approx. 1.6 kg on steel, a Ø20 x 5 mm approx. 4.9 kg and a Ø40 x 20 mm approx. 49 kg. That is the holding force under ideal conditions; in practice it is often half or less.
Holding force per size (disc magnets, N48)
Stated holding force of our NiCuNi disc magnets, measured perpendicular to a thick, flat steel plate:
| Size | Holding force (approx.) | Comparable to |
|---|---|---|
| Ø5 x 2 mm | 0.6 kg | a few A4 sheets on a whiteboard |
| Ø8 x 3 mm | 1.4 kg | a litre of milk |
| Ø10 x 3 mm | 1.6 kg | keeping a cabinet door closed |
| Ø10 x 5 mm | 3.1 kg | a small hammer |
| Ø15 x 5 mm | 4.3 kg | a (light) full shopping bag |
| Ø20 x 5 mm | 4.9 kg | a crate with 6 bottles |
| Ø20 x 10 mm | 12 kg | a full bucket of water |
| Ø30 x 10 mm | 17 kg | two pieces of cabin luggage |
| Ø40 x 20 mm | 49 kg | an adult dog |
You can find all sizes and values in the disc magnets, block magnets and pot magnets.
What determines how strong a neodymium magnet is?
- Thickness and diameter: the biggest factor. A Ø20 mm disc holds approx. 0.95 kg at 2 mm thickness, approx. 4.9 kg at 5 mm and approx. 12 kg at 10 mm. Thicker makes a big difference, until the thickness is about equal to the diameter.
- Grade (N35 to N52): an N52 is 20 to 40% stronger than an N35 of the same size. See what do N35, N42, N48 and N52 mean?
- Distance: the force drops quickly. With small magnets, 1 mm of distance (paint, film, cardboard) often already halves the holding force.
- The surface: thin steel (below approx. 2 – 3 mm), stainless steel, cast iron or a rough surface give less holding force. A magnet does not work on aluminium, copper and most types of stainless steel.
- Direction of the load: on a vertical wall a magnet already slides at 15 – 25% of the stated holding force. See holding force, pull force and working load.
- A steel pot: a pot magnet is often several times stronger at the same diameter. See why are pot magnets so strong?
Neodymium compared with other magnets
| Material | BHmax (energy product) | Max. temperature | Typical use |
|---|---|---|---|
| Neodymium (NdFeB) | 33 – 53 MGOe | 80 °C (special grades up to 200+ °C) | strong small magnets, motors |
| Samarium cobalt (SmCo) | 16 – 32 MGOe | 250 – 350 °C | high temperatures, aerospace |
| AlNiCo | 1.5 – 10 MGOe | 450 – 550 °C | sensors, guitar pickups |
| Ferrite (ceramic) | 1 – 4.5 MGOe | approx. 250 °C | fridge magnets, loudspeakers |
| Rubber magnet (flexible) | 0.6 – 1.5 MGOe | approx. 70 °C | magnetic sheet, advertising |
Why is neodymium so strong?
Neodymium magnets consist of the crystal compound Nd₂Fe₁₄B. It combines many iron atoms (high magnetisation) with a crystal structure that strongly locks the magnetisation in one direction. As a result, the material can deliver much more magnetic energy than ferrite at the same size. The material was developed simultaneously in 1982 – 1984 by Sumitomo (Japan) and General Motors (USA). Read more about the material in what is neodymium and where does it come from?
Frequently asked questions
How many kilos can a neodymium magnet carry?
From a few grams (Ø2 x 1 mm, approx. 0.13 kg) to hundreds of kilos (block 100 x 100 x 50 mm, approx. 800 kg). For a practical load, count on at most a third to half of the stated holding force, and even less on a vertical wall.
Are neodymium magnets dangerously strong?
Large neodymium magnets can slam into each other or into steel with great force, pinch fingers and shatter. Keep them away from children, pacemakers and bank cards. Read working safely with magnets.
Is a magnet with a higher Gauss value stronger?
Not necessarily. Gauss says something about the field at one point, not about the holding force. See what are Gauss and Tesla?
Read also
- How is the holding force of a magnet determined?
- Which disc magnet should you choose?
- Do magnets work through wood, glass and plastic?
Need help choosing? Use the Magnet Advisor or contact us.
