Magnet Pull Force Explained: What the Rating Means

Pull force is the force needed to pull a magnet straight off a thick, flat, polished steel plate with full contact, at room temperature. It's a laboratory value: from supplier data, or for magnets without supplier data a calculated estimate marked "approx., calculated". In real use a magnet holds less, often considerably less, because of air gaps, thin or rough steel, sideways loads, heat and vibration.

Pull force at a glance

Factor What happens to the holding force What to do
Test conditions Straight pull, thick polished steel, full contact, room temperature: the best case Treat the listed value as an upper limit
Air gap (paint, powder coating, rust, dirt, tape, labels, paper, rubber coating) Drops sharply; even a fraction of a millimetre is noticeable, especially for small magnets and pot magnets Get bare, direct contact where you can
Thin steel sheet Holds much less than on a thick plate, because thin steel can't absorb the full field Use a steel counter-plate, or test on the real sheet
Type of steel Mild steel is best; cast iron, alloyed and hardened steel give less; most stainless steel (304, 316) is barely or not magnetic Check the surface with a magnet first
Rough, curved or partial contact Lower force Flat, full-face contact
Sideways (shear) load The magnet slides off at a much lower force than its rating Support from below, add magnets, use rubber-coated magnets
Temperature Warmer means weaker: about 0.12% of remanence per °C, reversible up to the rated temperature; standard grades are rated to 80 °C (176 °F) Check the max. temperature on the product page
Vibration, shocks, repeated loading Can make a magnet let go well below its rating Allow a generous safety margin and test
Magnet to magnet Differs from magnet to steel and depends on both magnets Test the actual pair

How pull force is measured

The pull force we list (also called holding force or adhesive force) is an indicative value in kilograms. It's the force needed to pull the magnet straight off a flat, polished steel plate that's thick enough not to limit the result, with the whole magnet face in contact, at room temperature. Where a supplier value exists, it comes from our suppliers' data and is measured under ideal conditions. For magnets without supplier data, the product page shows a calculated estimate instead: we calculate it from the magnet's grade and dimensions, based on our supplier values for magnets of the same shape. It's labelled "Pull force (calculated estimate)" and "approx. … kg, calculated", and it never replaces a supplier value. Real holding force varies and can differ from the estimate.

That's why the same number can't simply be read as "this magnet holds X kg on my door". It's the best case, defined the same way for every magnet, so it's useful for comparing magnets with each other, not as a promise for your application.

Why your magnet holds less than its rating

Air gap. Anything between the magnet and the steel acts as a gap: paint, powder coating, rust, dirt, tape, a label, a sheet of paper, cardboard, or the magnet's own rubber coating. The force falls sharply with distance. Even a gap of a fraction of a millimetre makes a noticeable difference, especially with small magnets and pot magnets.

Thin steel. A thin steel sheet, such as a fridge door, a cabinet panel or a whiteboard, can't absorb the full magnetic field. A strong magnet holds much less on it than on a thick plate.

The wrong steel. Low-carbon (mild) steel gives the best result. Cast iron and alloyed or hardened steels give less. Most stainless steels, including the common grades 304 and 316, are barely magnetic or not magnetic at all. Aluminium, copper, brass, wood, glass and plastic aren't magnetic.

Shear (sideways loads). The rating applies to a straight, perpendicular pull. A sign on a wall, a tool on a vertical steel panel or anything hung on a door loads the magnet sideways instead. In that direction friction does the holding, and the magnet slides at a much lower force than its rating. Rubber-coated magnets resist sliding better, though the rubber also acts as a small air gap.

Heat. All neodymium magnets get weaker as they warm up, by about 0.12% of their remanence per °C. Up to the rated temperature this loss is reversible. Standard grades are rated to 80 °C (176 °F); grades with a suffix (M, H, SH, UH, EH, AH) go higher. See N35 vs N42 vs N52 explained.

Vibration and shocks. Vibration, knocks and repeated loading can make a magnet let go well below its rated force.

How to read the pull force on our product pages

Magnets with supplier data show their pull force in the specification table, for example:

"Approx." is there because these are indicative supplier values. Magnets without supplier data show a separate row, "Pull force (calculated estimate)", for example Neodymium Sphere Magnet 25 mm N48: approx. 10 kg, calculated. Treat an estimate as a rough guide and test before relying on it. To compare magnets by load, use our magnet pull force chart, which lists 344 magnets with supplier values from 0.16 kg to 230 kg, plus 540 calculated estimates, each marked as such.

Pot magnets, hook magnets and eyebolt magnets have a steel housing that concentrates the field on the open face. They're the usual choice for fixing and hanging: see pot magnets and hook and eyebolt magnets.

Before choosing, see how to choose a magnet.

Safety: strong magnets can pinch fingers and skin, and can chip or shatter if they snap together. Keep them away from pacemakers and other medical implants. Our products are not toys: keep small magnets out of the reach of children. See our magnet safety page.

Questions and answers

What does pull force mean on a magnet?

It's the force needed to pull the magnet straight off a thick, flat, polished steel plate with full contact, at room temperature. It's a best-case laboratory value, from supplier data where we have it.

How is magnet pull force measured?

By pulling the magnet straight away from a steel plate that's thick enough not to limit the result, with the whole face in contact, and recording the force at which it lets go.

Is holding force the same as pull force?

Yes. Pull force, holding force and adhesive force are used for the same rating.

What is the difference between pull force and shear force?

Pull force is a straight, perpendicular pull. Shear is a sideways load, for example a weight hanging from a magnet on a vertical wall. In shear the magnet slides off at a much lower force than its pull-force rating.

Why is there no magnet pull force calculator here?

Because the real holding force depends on your gap, steel thickness, steel type, load direction, temperature and vibration. We list the supplier value where we have one, and for magnets without supplier data a calculated estimate for the ideal case, clearly marked "approx., calculated". Neither tells you what the magnet will hold in your setup, so we explain what lowers it instead of offering a calculator for your application. Test in your own application and allow a generous safety margin.

Does pull force drop with distance?

Yes, sharply. Any gap, including paint, a coating or a sheet of paper, lowers the force, and even a fraction of a millimetre is noticeable.

Is gauss the same as pull force?

No. Surface field strength (gauss or mT) is the field measured at the magnet's surface. It isn't the same as pull force.

Do two magnets stuck together hold with their listed pull force?

Not necessarily. The force between two magnets differs from the force between a magnet and steel, and depends on both magnets.

Can I use magnets to hold things overhead?

Don't use magnets on their own to hold loads above people, or anywhere failure could cause injury or damage, unless the design has been checked and tested by a qualified person.

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