A gap between a magnet and its counterpart can reduce the force available in an assembly. Include coatings, packaging layers and clearance in your specification.
A gap is not always visible air
Card, plastic, paint, an adhesive layer or an uneven surface can separate the magnet from its counterpart. Measure the total separation in the finished design rather than judging only the visible space between components.
Why a catalogue pull figure is not enough
A pull figure depends on the test arrangement, including the magnet, mating material and contact conditions. A part tested against a flat steel surface may behave differently when installed behind a panel or used across a gap. The effect is not a single fixed percentage for all magnet shapes and assemblies.
Describe the real geometry
- Magnet shape, dimensions and magnetisation direction.
- Whether the counterpart is steel or another magnet.
- Steel thickness or the second magnet’s specification.
- Minimum and maximum gap, including all intervening layers.
- Whether the load pulls away, slides sideways or peels from an edge.
Validate the assembly
Use a calculation only when its geometry and assumptions match the design. Test candidate parts with the intended materials, gap and load direction before fixing a production specification. If the closure is adjustable, test the least favourable tolerance position as well as the nominal one.
Read our magnet strength guide for pull versus sliding loads. Compare disc magnets and block magnets, or use the custom magnet calculator when an existing size does not fit. contact magnets direct with a drawing and the expected gap to discuss the specification.
Technical reference: supermagnete explanation of factors affecting magnetic attraction.