Magnet Pull Force Calculator
Estimate how hard a neodymium magnet holds to steel or to another magnet, and see its surface field. Enter the size and grade of a disc, ring, block or sphere magnet, then add a gap, thin steel or heat to see how its pull force changes.
The calculator needs JavaScript to run. The tables below show pull forces for popular sizes in common setups.
- Shapes
- Disc, Cylinder, Ring, Block, Cube, Bar and Sphere
- Grades
- N35 to N52, Plus N42SH
- Adjusts For
- Gap, Steel Thickness and Temperature
- Results In
- lb, kg or Newtons, Plus Gauss
How to Use the Pull Force Calculator
- Choose the shape and enter its size in inches or millimeters. Use Disc for cylinders and rods, and Block for cubes and bars. Thickness is measured pole to pole, along the magnetization direction.
- Pick the grade, from N35 to N52, or N42SH for heat. Every product page lists the grade. See N42 vs. N52 magnets.
- Choose what the magnet holds to: steel, with its thickness, or an identical magnet. A fridge door or other thin sheet steel holds less than a thick plate.
- Add the gap. Anything between the magnet and the steel counts, such as paint, fabric, cardboard, wood, plastic or drywall. Drag the slider, type a value or tap a preset.
- Set the temperature if the magnet will run warm, up to the 176°F (80°C) limit of standard grades.
- Read the results. You'll see the straight pull force, how much the magnet holds on a vertical wall before it slides, and its pull at contact, plus its surface field in gauss. Select the Magnetic Field preview under the side view to open a full map of the field lines around the magnet, colored by strength, then point anywhere on it to read the field there. Below that, the closest magnets we stock show what each one pulls in the same setup.
What Pull Force Means
Pull force is the force needed to pull a magnet straight off a thick, flat steel plate with nothing in between. It's the magnet's best-case holding force, measured the same way for every magnet so you can compare one with another. See how pull force is measured.
How much a magnet actually holds depends on which way the load acts:
Straight Pull
A load that pulls straight away from the steel, like a sign hanging below a beam. The magnet can hold up to its full pull force.
Sliding on a Wall
On a vertical surface, only friction holds the load, so a magnet slides at about 15 to 25% of its pull force. See shear force.
Magnet to Magnet
Two identical magnets touching pull about as hard as one magnet on thick steel. Across a gap, the pair holds more. See magnet-to-magnet vs. magnet-to-steel.
What Lowers Pull Force
A magnet reaches its listed pull force only in the rating test. In a real project, these lower it:
| Factor | What Happens | In the Calculator |
|---|---|---|
| Gap | Paint, fabric, wood, plastic and other materials act like air. Pull drops fast: 1/16 in (1.6 mm) leaves a 1/2 × 1/8 Inch disc with about 30% of its rating. See air gaps. | Gap |
| Thin steel | Sheet steel saturates and can't carry all of the magnet's field. Large magnets lose the most. See steel thickness. | Steel Thickness |
| Vertical surfaces | The load slides instead of pulling straight off, and friction holds only about 15 to 25% of the pull force. | On a Vertical Wall |
| Heat | A warm magnet is weaker until it cools. Standard N grades lose strength for good above 176°F (80°C). | Temperature |
| Surface and steel type | Rough, rusty, curved or painted steel leaves tiny gaps. High-carbon and stainless steels hold less than mild steel. | Not included, so test it |
Example: One Magnet in Different Setups
Here's how the calculator estimates a 1/2 × 1/8 Inch N52 Disc, listed at 8.15 lb (3.70 kg), in common situations:
| Setup | Pull Force | Share of Rating |
|---|---|---|
| Thick steel, direct contact (the listed rating) | 8.15 lb 3.70 kg |
100% |
| Through paint, about 0.1 mm (0.004 in) | 7.3 lb 3.30 kg |
89% |
| Through a business card, about 0.3 mm (0.012 in) | 6.0 lb 2.73 kg |
74% |
| Through 1/32 in (0.8 mm) of fabric or paper | 4.1 lb 1.85 kg |
50% |
| Through 1/16 in (1.6 mm) of felt or cardboard | 2.5 lb 1.11 kg |
30% |
| Through 1/8 in (3.2 mm) of thin wood or acrylic | 1.1 lb 0.48 kg |
13% |
| On a fridge door (24-gauge steel, 0.6 mm) | 4.1 lb 1.88 kg |
51% |
| At 176°F (80°C), while it's hot | 7.0 lb 3.18 kg |
86% |
| On a vertical steel wall, before it slides | 1.2 to 2.0 lb 0.55 to 0.92 kg |
15 to 25% |
Pull Force for Popular Magnet Sizes
Listed pull force and surface field from our catalog, with what the calculator estimates through a 1/16 in (1.6 mm) gap, on a fridge door (24-gauge steel, 0.6 mm) and on a vertical steel wall. Select Open in Calculator to try any size in your own setup.
| Magnet | Listed Pull Force | Surface Field | Through 1/16 in | On a Fridge Door | Slides on a Wall At |
|---|---|---|---|---|---|
|
1/4 × 1/8 Inch N52 Disc Open in Calculator |
2.9 lb 1.32 kg |
5,227 G | 0.52 lb | 2.4 lb | 0.43 to 0.72 lb |
|
1/2 × 1/8 Inch N52 Disc Open in Calculator |
8.15 lb 3.70 kg |
3,315 G | 2.5 lb | 4.1 lb | 1.2 to 2.0 lb |
|
3/4 × 1/8 Inch N52 Disc Open in Calculator |
12.1 lb 5.49 kg |
2,340 G | 4.3 lb | 5.0 lb | 1.8 to 3.0 lb |
|
1 × 1/4 Inch N52 Disc Open in Calculator |
33.7 lb 15.3 kg |
3,350 G | 16.1 lb | 8.4 lb | 5.1 to 8.4 lb |
|
1 × 1/2 Inch N52 Disc Open in Calculator |
54.5 lb 24.7 kg |
5,233 G | 29.8 lb | 10.7 lb | 8.2 to 13.6 lb |
|
1/2 × 1/2 Inch N52 Cylinder Open in Calculator |
18.1 lb 8.21 kg |
6,620 G | 7.3 lb | 6.2 lb | 2.7 to 4.5 lb |
|
3/4 × 1/4 × 1/4 Inch N52 Ring Open in Calculator |
21.8 lb 9.89 kg |
2,512 G | 7.6 lb | 7.2 lb | 3.3 to 5.5 lb |
|
3/4 × 1/4 × 1/8 Inch N52 Bar Open in Calculator |
7.8 lb 3.54 kg |
3,935 G | 2.0 lb | 5.2 lb | 1.2 to 1.9 lb |
|
1/2 Inch N52 Cube Open in Calculator |
23.2 lb 10.5 kg |
6,451 G | 9.9 lb | 7.9 lb | 3.5 to 5.8 lb |
|
1/2 Inch N52 Sphere Open in Calculator |
8.1 lb 3.67 kg |
9,867 G | 3.3 lb | 4.1 lb | 1.2 to 2.0 lb |
Shop by shape: Disc Magnets, Cylinder Magnets, Ring Magnets, Block Magnets, Cube Magnets and Sphere Magnets.
How Much Pull Force Do You Need?
Add up the listed pull force of all your magnets and compare it with the weight of the item:
Pulls Straight Off the Steel
Hanging below a shelf, beam or steel ceiling: aim for at least 1.5× the weight in total pull force. A 5 lb sign needs about 7.5 lb.
Slides on a Vertical Surface
On a wall, door, fridge or cabinet side: aim for 7 to 10× the weight, using 10× on thin sheet steel. A 5 lb tool needs 35 to 50 lb.
Add more for any gap, and for vibration or bumps. Using more than one magnet? Divide the total by the number of magnets to get the pull force each one needs, and spread them out so they share the load. Our guide How Many Magnets Do I Need to Hold My Item? has a calculator that does this math for our most popular discs.
Overhead and Safety-Critical Loads
Don't rely on magnets alone where a sliding or falling item could hurt someone or damage property. Add a ledge, mechanical fastener or safety cable.
How the Calculator Works
The calculator uses a physics model of the magnet, adjusted for the steel, the temperature and how the load acts.
- Magnetic model. Each pole face is treated as a sheet of magnetic charge, and thick steel acts as a magnetic mirror, so a magnet on steel pulls like it would on an identical twin magnet (the method of images). Disc and ring forces are integrated numerically, blocks use the exact closed-form solution for rectangular faces, and a sphere acts as a point magnet at its center.
- Thin steel is estimated from how much magnetic flux low-carbon steel can carry before it saturates, matched to the figures in our steel thickness guide.
- Temperature lowers the magnet's strength by about 0.12% per °C above 68°F (20°C), which costs about 14% of its pull at 176°F (80°C). Within the grade's rating, the loss reverses as the magnet cools.
- Surface field is the field at the center of the pole face, shown in gauss (G) and millitesla (mT). It's worked out from the magnet's dimensions and grade, and like pull force it drops a little as the magnet warms. For a ring, that point is in the center of the hole. The field map is worked out the same way, from exact formulas for each shape, for the magnet on its own away from steel, and it's scaled to match the surface field reading.
- On a vertical wall shows 15 to 25% of the pull force, the typical friction range for a nickel-plated magnet on clean, dry steel.
What the Calculator Doesn't Cover
Results are estimates for clean, flat, smooth, low-carbon steel with the pole face flat against it. Pulling at an angle, rough or curved surfaces and other steel types all lower the real pull. Diametric, countersunk, pot and plastic- or rubber-coated magnets aren't modeled, so use the rating on their product pages. For a stack of identical magnets, enter the stack's total thickness. Always test with your own materials before relying on a magnet.
Need a Size We Don't List?
We make custom neodymium magnets in your size, grade and coating. Send us your dimensions and the pull force you need, and we'll reply by email with a quote.
Request a Custom QuoteShop Disc MagnetsPull Force FAQs
How accurate is this pull force calculator?
The calculator's results come from a mix of pull testing and mathematical modeling. Real-world results will vary with the steel, the surface and the direction of the load, so take these numbers as a starting point, and always do your own testing before relying on a magnet.
How much weight can a neodymium magnet hold?
Up to its listed pull force, but only when the load pulls straight off thick, flat steel with nothing in between. Allowing a safety margin, plan on about two-thirds of the rating when the item hangs below thick steel, and about a seventh to a tenth of it on a vertical wall. See does a 20 lb magnet hold 20 lb?
How much does a gap reduce magnet pull force?
A lot, and small magnets lose the most. A 1/2 × 1/8 Inch N52 disc keeps about 50% of its pull through 1/32 in (0.8 mm), 30% through 1/16 in (1.6 mm) and 13% through 1/8 in (3.2 mm). A larger 1 × 1/2 Inch N52 disc keeps about 55% through 1/16 in and 35% through 1/8 in. Enter your gap in the calculator to see your magnet's curve.
Why does my magnet hold less on a fridge?
A fridge door is thin, painted sheet steel, and it's vertical. Thin steel saturates: a 1/2 × 1/8 Inch N52 disc keeps about 51% of its 8.15 lb rating on 24-gauge steel, and a 1 × 1/2 Inch disc only about 20%. The load also slides instead of pulling straight off, so the magnet holds only 15 to 25% of that. Several small magnets usually beat one large one on thin steel.
Is N52 stronger than N42?
Yes. For the same size, an N52 magnet pulls about 25% harder than N42 and nearly 50% harder than N35, because pull force rises with the square of the material's remanence. A slightly thicker N42 magnet often matches an N52. See N42 vs. N52 magnets.
What is surface field, and how is it different from pull force?
Surface field is the strength of the magnetic field at the center of a magnet's pole face, measured in gauss (G). It describes the field at one point, not the holding force. Magnets with the same proportions have about the same surface field at any size: a 1/4 × 1/8 Inch N52 disc and a 1 × 1/2 Inch N52 disc both measure about 5,230 gauss, yet the larger one pulls 54.5 lb to the smaller one's 2.9 lb. Use pull force to compare holding power, and surface field for sensors and field specs. See gauss vs. pull force.
Does temperature affect magnet pull force?
Yes. A neodymium magnet's field weakens by about 0.12% for every °C it warms, so a standard N-grade magnet pulls about 14% less at 176°F (80°C) than at room temperature, and it recovers as it cools. Above its rated temperature it loses strength for good. For hot locations, choose a high-temperature grade such as N42SH, rated to 302°F (150°C). See moisture and temperature.
Is magnet-to-magnet stronger than magnet-to-steel?
When they touch, about the same: a pair of identical magnets pulls about as hard as one magnet on thick steel. Across a gap, the pair wins, because a gap to steel acts like twice that gap between two magnets. Through 1/8 in, two 1/2 × 1/8 Inch N52 discs hold about 2.5 lb, while one disc on thick steel holds about 1.1 lb. Choose An Identical Magnet in the calculator to compare.
Can I calculate pull force for cylinder, cube and bar magnets?
Yes. Use Disc for cylinders and rods, entering the length as the thickness when the magnet is magnetized through its length. Use Block for cubes and bars. Rings and spheres have their own settings.
Does the calculator work for countersunk, pot or coated magnets?
Not exactly. Countersunk holes, the steel cup of a pot magnet and plastic or rubber coatings change the pull in ways the model doesn't cover, so use the rating on the product page. See why pot magnets are stronger.
Where do your listed pull force ratings come from?
Depending on the product, from our own pull testing, from our manufacturer's test data or from calculations based on the magnet's size and grade. All of them describe the same standard test: a straight pull off a thick, flat, ground steel plate with no gap. See how pull force is measured.
Sources
- G. Akoun and J.-P. Yonnet, “3D analytical calculation of the forces exerted between two cuboidal magnets,” IEEE Transactions on Magnetics, vol. 20, no. 5, 1984.
- E. P. Furlani, Permanent Magnet and Electromechanical Devices: Materials, Analysis, and Applications, Academic Press, 2001.
- N. Derby and S. Olbert, “Cylindrical magnets and ideal solenoids,” American Journal of Physics, vol. 78, no. 3, 2010.
- Listed pull force ratings for totalElement bare, axially magnetized neodymium magnets, checked October 2026.