Magnet Pull Force Calculator

Inputs

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Magnet grade (grade)

Representative remanence values for common permanent-magnet materials. Use supplier data when you have it.

Magnet shape (shape)

Shape only sets the pole area. Magnetization is assumed through the thickness.

Diameter (d)

Circular pole diameter for a disc or cylinder magnet.

Magnet thickness (t)

Magnet dimension in the magnetization direction.

Air gap / coating (g)

Effective nonmagnetic gap from air, paint, plating, adhesive, unevenness or protective film.

Circuit efficiency (k_c)

Derates Br to a practical contact-face flux density. Lower it for thin magnets, open flux paths and non-ideal geometry.

Target/contact factor (k_t)

Derates pull for steel thickness, surface finish, roughness, paint, curvature, edge fringing and nonuniform contact.

Safety factor (SF)

Pull force is divided by this value to estimate a safe working load.

Results

Default result

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Safe working load(SWL)

17.64N

Pass

3.966 lbf

Also computed

Estimated pull force(F_pull)52.92N

11.9 lbf

Equivalent held mass(m_hold)1.799kg

Gap flux density(B_gap)0.84T

Contact flux density(B_contact)0.924T

Gap derating(k_g²)82.64%

Pole area(A)314.2mm²

Small gaps, paint, coatings and surface roughness dominate permanent-magnet pull force. Use the curve to see how quickly the screening force falls with clearance.

Method notes 3 notes

Screening model uses B_gap = Br*k_c*t/(t+g), then F = B_gap^2*A*k_t/(2*mu0).
Grade Br values are representative; supplier pull-force data or measured tests should control final selection.
Real pull depends on magnetization direction, keeper geometry, steel thickness, edge fringing, temperature, coatings, sliding/shear loads and the magnet B-H curve.