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What formula can be used to calculate the magnetic force of NdFeB permanent magnets

The pull force of N35 grade neodymium magnets depends on several factors, such as the size and shape of the magnet, the distance between the magnet and the ferromagnetic material it's attracting, and the orientation of the magnet's poles relative to the material.

As a general rule of thumb, the pull force of a neodymium magnet can be estimated using the following formula:

F = (B^2 * A) / (2 * μ0)

Where:

F is the pull force in Newtons (N)

B is the magnetic field strength of the magnet in Tesla (T)

A is the surface area of the magnet in square meters (m^2)

μ0 is the magnetic constant, which has a value of 4π x 10^-7 Tm/A.

It's important to note that this formula provides an approximation of the magnetic force, as it assumes that the magnetic field is uniform over the entire surface of the magnet, which may not be the case in all situations. Also, the shape and size of the magnet can affect the magnetic force, so this formula may not be accurate for all NdFeB magnets.

Caculate Proess:
Example: Magnet: N35 NdFeB Magent, Size: 30mm×15mm×5mm, Shape:block.

Let's assume that the magnetic field strength of the N35 NdFeB magnet is 1.3 Tesla (T).

The surface area of the magnet can be calculated as:

A = 2 * (30mm x 15mm + 30mm x 5mm + 15mm x 5mm) = 1950 mm^2 = 0.00195 m^2

Using the formula:

F = (B^2 * A) / (2 * μ0)

F = (1.3 T)^2 * 0.00195 m^2 / (2 * 4π x 10^-7 Tm/A)

F ≈ 20.7 Newtons (N)

More example for pull force of N35 grade neodymium magnets

N35 neodymium magnet with a diameter of 1 inch (25.4mm) and a thickness of 1/8 inch (3.175mm), with a pull force of approximately 7.3 pounds (3.3 kg).

N35 neodymium magnet with a diameter of 3/4 inch (19.05mm) and a thickness of 1/4 inch (6.35mm), with a pull force of approximately 12.8 pounds (5.8 kg).

N35 neodymium magnet with a length of 2 inches (50.8mm), a width of 1 inch (25.4mm), and a thickness of 1/4 inch (6.35mm), with a pull force of approximately 72.8 pounds (33 kg).

N35 neodymium magnet with a diameter of 1/2 inch (12.7mm) and a thickness of 1/16 inch (1.588mm), with a pull force of approximately 1.1 pounds (0.5 kg).

Other simple way to caculate pull force(based on usual experience, not always correct)

Take the square NdFeB magnet as an example, its grade is: N38, specification: 30mm×15mm×5mm.

1. Permanent magnet density: The approximate density of N38 is about 7.5 grams per cubic centimeter.

2. Weight of permanent magnet: volume × density (30mm × 15mm × 5mm) × 0.0075=16.875 grams

3. The suction force of the permanent magnet: 16.875×600=10125 grams

Permanent magnet suction calculation formula: Magnet volume × density × 600 (multiple) = suction

It can be known that a 30mm×15mm×5mm square permanent magnet can pick up about 10.125kg of material.