Surface Field & Pull Force Calculator

Enter a magnet's shape, size and grade to estimate its surface field (mT / gauss) and pull force range.

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Engineer check on request

1Magnet

Shape

Top view (pole face)

Cross-section

T is the thickness along the magnetisation (arrow, S→N inside the magnet); D, L × W or OD / ID are across it. Labels show the values entered.

Grade

Diameter D

Thickness (magnetised) T

2Measurement & working temperature

Measuring distance

Gaussmeter probe distance from the pole face, over the centre (ring: over the middle of the wall); 0 = on the surface.Working temperature

°C

Temperature the magnet actually works at.

3Steel it sticks to

Air gap to steel

Gap between magnet and steel, e.g. tape, plastic or paint.Steel plate thickness

Thickness of the steel it holds; thinner steel holds less.

Surface field 410–423 mT ≈ 4,105–4,232 Gs|Pull force 16.3–26.1 N

Surface field

410–423 mT

≈ 4,105–4,232 Gs

Centre of the pole face · includes the industry 0.9 factor — enter the real measuring distance · at 20 °C

Pull force

16.3–26.1 N

≈ 1.67–2.66 kg

Pull-off force perpendicular to flat mild steel (upper end = best case) · at 20 °C

Sliding hold on a vertical steel surface is only ~20–30 % of this.

Estimates (theory with an empirical 0.9 factor on surface field) for preliminary selection only. Temperature is applied as a reversible Br change; the grade's max working temperature (80 °C) is a catalogue value and must be checked against the magnet's working point (thin magnets demagnetise at lower temperatures). Pull assumes clean, flat mild steel of the thickness entered; plate saturation is a simplified estimate.

Need measured data? Contact our engineers

Field around the magnet

Field lines and |B| — section through the axis (at maximum Br)

01 T

Ideal uniformly magnetised magnet, N face up. Shading is flux density on a square-root scale (so the weak fringe field stays visible); lines are field lines. The dot marks the measuring point.

Field against measuring distance

0 mm · 410–423 mT

Same basis as the result above (industry 0.9 factor included); band = grade Br min–max at the working temperature.

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