Electromagnet Holding Force Calculator

Inputs

Flux density at pole (B)

Measured or estimated normal flux density at the working pole face.

Pole width (w)

Effective rectangular pole contact width.

Pole length (l)

Effective rectangular pole contact length.

Active poles (n_p)

Number of pole faces carrying useful normal flux.

Contact factor (k_c)

Derating for rough surface, paint, scale, air gap, thin backing steel, leakage and nonuniform flux.

Safety factor (SF)

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

Default result

Safe working load(SWL)

458.4N

Pass

103 lbf

Also computed

Derated holding force(F_hold)1,375N

309.1 lbf

Equivalent held mass(m_hold)46.74kg

Force per pole(F_pole)687.5N

Magnetic pressure(p_m)0.573MPa

Total pole area(A)4,000mm²

Contact factor used(k_c)60%

Holding force scales with the square of flux density, so small field losses from gap, paint or rough contact can remove a lot of load capacity.

Method notes 3 notes

Holding force uses magnetic pressure p = B^2/(2*mu0), multiplied by total pole area and contact factor.
Safe working load divides the derated holding force by the entered safety factor.
Paint, rust, curved parts, thin backing steel, air gaps, vibration and sliding loads can reduce real holding force sharply. Test safety-critical lifts.