Magnet force and induction calculator — v1
On-axis field, mass and estimated force for simple shapes
Calculator v1 estimates magnetic induction on the magnet axis in air and mass from dimensions. For cylindrical and block magnets it also estimates pull force against an ideal steel plate. It does not model steel-cased holders or complete magnetic assemblies.
Select the grade and dimensions in millimetres. Distance is measured from the surface, including the coating. The bore affects the ring field; this version does not report pull force for rings or spheres. Results are model estimates, not measurements or rated working loads.
Select the grade and dimensions in millimetres. Distance is measured from the surface, including the coating. The bore affects the ring field; this version does not report pull force for rings or spheres. Results are model estimates, not measurements or rated working loads.
Select a magnet shape below to start calculations:
0–50 mm from the magnet surface; the model adds the selected coating offset.
| magnet grade properties: | |||||
|---|---|---|---|---|---|
| system: | CGS | SI | |||
| grade: | |||||
| remanence: | (Br) | kGauss | mT | ||
| coercivity: | (Hcb) | kOe | kA/m | ||
| intrinsic coercivity: | (Hcj) | kOe | kA/m | ||
| energy density: | (BH Max.) | MGOe | kJ/m³ | ||
| max. working temp.: | °C | ||||
Remember that the final pull force (besides just the thickness of the magnet) is also influenced by:
- material grade (e.g. N38 vs N52),
- potential magnetic assemblies (e.g. closing the circuit with steel).
- magnet shape and contact surface area (the larger, the better),
- the magnet's own weight,
The grade number refers to the maximum energy product (BHmax), not directly to pull force. Compare remanence, coercivity and operating temperature in the table. A higher number does not replace selecting suitable geometry and operating conditions.
On-axis field uses analytical formulas for uniformly magnetized cylinders, blocks, rings or spheres. Pull force for cylinders and blocks uses a Maxwell-stress model with an empirical correction and a field limit. It is not interpolation of a measurement database or simulation of a complete mounting. Pull force is not reported for rings or spheres.
Do not equate pull-off force with a rated working load. Thin steel, paint, gaps and sideways loading may reduce force. Select secondary retention and a safety factor for the application, then test on the actual substrate.
See also
- neodymium magnet pull force calculator - breakaway force including shape and surface
- magnetic moment calculator - magnetic moment in A·m² for comparing magnets
- permeance coefficient calculator - the operating point set by the dimension ratio