We have a lot of customers will often ask us the weight of the magnet, used to calculate the freight price. Generally, in addition to the weight of the magnet itself, we will also need to add the weight of magnetic insulation materials and packaging for export.

There are many different kinds of magnets, such as sintered neodymium magnets, sintered samarium cobalt magnets, bonded neodymium magnets, sintered ferrite magnets, aluminum nickel cobalt magnets, injection ferrite magnetss,  iron chromium cobalt magnets and so on. The production process of these magnets is not the same, and even the material formula ratio of each magnet manufacturer is not the same, which will lead to different density of magnets. In general, the lower the grade or density of the magnet, the lighter the weight of the magnet.

Different materials will lead to different density of magnets, such as the density of sintered NdFeb is 7.5g /cm³, such as bonded NdFeb 6 g/cm³, the density of sintered ferrite magnet is 4.9g /cm³, injection ferrite 3.8g /cm³.

Here I will introduce how to accurately calculate the weight of Neodymium magnet with a formula, and share with you the weight calculation formula of Neodymium magnet with different shapes. The mass calculation formula of a single magnet is: mass = density x volume, that is, m (g) =ρ (g/cm³) x V(cm³), and then multiplied by the total number can calculate the total weight.

Weight calculation formula of sintered Neodymium block magnet: (density calculated by 7.5)

For example: F10x5x2mm sintered Neodymium block

The calculation formula is: Length x Width x Height /1000= Weight (g).

The calculation formula is: 10x5x2x7.5/1000=13.3g.

Weight calculation formula of sintered Neodymium disc magnet: (density calculated at 7.5)

For example: D10x2mm neodymium circular magnet

The calculation formula is: Area x Thickness x Density /1000= Weight (g).

3.14 * 10² *2*7.5 /4000 = 1.18g or 3.14 * 5² * 2*7.5/1000 = 1.18g.

Weight calculation formula of sintered Neodymium ring magnet (density calculated at 7.5)

For example: D10 x d8 x 2 mm sintered neodymium ring magnet

The calculation formula is: Π * (a + b) (a - b) * c (thickness) * p (density) / 4000 ( a=outer diameter, b =inner diameter) 

3.14x (10+8) x (10-8) x2x 7.5/4000 = 0.42g

For neodymium arc segmented magnets, the calculation formula is a bit complex, and I won't be able to calculate it yet.

Curved strong magnets of various sizes used in motor

The above introduces the weight calculation method for sintered rare earth neodymium magnet rings/disc/block. If it is not made of neodymium material, the density value needs to be changed, as described above. 

Related magnet weight calculation article;

How to calculate weight by knowing the size of ferrite ring magnets?