Calculator
Estimate surface magnetic field (GS) and pull force for disc, ring, square and block neodymium magnets — adjust shape, dimensions, grade and steel thickness. Analytical model with a hook for real measured data.
The calculator returns two numbers and two curves for the configuration you entered.
Pull force is the holding force between the magnet and a steel plate, printed in kgf, N and lbf. Compare it with the load in your application and then apply your own safety factor: a real assembly is affected by coating thickness, surface flatness and off-axis loading.
Surface field (GS) is the flux density at the working face, in Gauss — and the tool also plots the value at a stand-off, so you can match a gauss-meter reading instead of only the on-contact figure.
Five inputs move the result the most, and their order matters more than the exact numbers.
Pull force scales with Br², so a small gain in remanence is amplified. Our N35 (Br 11.8 kG) and N52 (Br 14.2 kG) differ by about 20 % in Br but roughly 45 % in force.
Force is proportional to the pole face area in contact with the steel. Thickness helps until the magnet works at its operating point — past that, extra thickness adds cost rather than grip.
A thin plate saturates and steals force. In the tool a 1 mm plate returns about 0.85× the force of a saturated plate for the same magnet, which is why steel thickness is an input here (0.5–3 mm) and why anything above 3 mm is treated as saturated steel.
Every extra tenth of a millimetre of effective gap costs pull force, and plating is never zero. The 0.03 mm default allows for nickel-copper-nickel plating, steel coating and surface flatness — replace it with the real value of your assembly.
Br falls as temperature rises; stay below the grade’s maximum working temperature (80 °C for standard N grades — use M/H/SH/UH/EH/AH where your design runs hotter). Axial (flat face) and radial (arc face) magnets also pull differently, because the radial mode clamps to a curved surface.
Enter these in the form to reproduce them. All three sit inside our sampled grid, so the tool answers from its measured pool instead of extrapolating.
A small round magnet on a thick plate: the reference case for comparing against a datasheet.
Thin-plate case. The tool applies a ≈0.85× steel factor because the plate saturates — useful when your housing is a thin sheet.
Ring magnets on a curved surface. Most online magnet calculators stop at discs and blocks; this one covers rings, spheres and radial magnetization.
The baseline is a closed-form attraction model between a magnet face and a steel plate (field to force via F = B²·A / 2µ₀), so a result exists for any size you type, not only for catalogue sizes.
Where an interpolated point falls outside our ±20 % band against the reference data, the tool withholds the number instead of printing a guess.
For discs, reference points at D20 × 5 mm (N35 = 47.71 N, N42 = 58.18 N, N52 = 69.92 N on saturated steel with no gap) calibrate the model, and additional pull-test data can replace or extend them.
Results assume a clean, flat, sufficiently large steel plate, contact through a thin non-magnetic layer and room temperature. Finite plates, eccentric loading, adhesive joints and elevated temperature all reduce the real value — which is why the output is a selection estimate and why we offer measurement.
Send us your shape, size, grade, coating and the steel it will stick to. We measure pull force and field for your configuration on our own rig and share the data — so your decision is based on the part you actually ship, not on a catalogue value.
Enter the shape, dimensions, grade, steel thickness and gap. The calculator returns the holding force in kgf, N and lbf for that configuration, plus the surface field in Gauss and a curve of force versus steel thickness.
Up to a point: the plate must carry the flux without saturating. The tool applies a steel factor between 0.5 mm and 3 mm and treats anything above 3 mm as saturated steel.
Noticeably, and not linearly. That is why gap is an input in millimetres and the result includes a distance curve — on-contact catalogue values overstate what a real assembly holds.
They come from an analytical model + a simulation sample pool (calibrated against measured anchors). Interpolated points outside our ±20 % band are withheld rather than guessed. Treat the output as a selection estimate and verify critical joints by test.
Yes — disc, ring, block/rectangle and sphere shapes are covered, with both axial (flat face) and radial (arc face) magnetization.
Gauss, the CGS unit of flux density: 1 T = 10,000 Gs. The tool prints Gauss and also the value at a distance, so you can compare it with a gauss-meter reading.