The Magnet Playground

an engineering tool for permanent magnet design

Design a Magnet
Pick the general 3D shape of the magnet.

Pick the magnetic material. See the materials tab for detailed options.

mm
mm
mm
Through which dimension is the magnet magnetized? This tools is for anisotropic magnets only, magnets with a single direction of magnetization.
mm
mm
This is the height of the cylinder or ring. mm

Through which dimension is the magnet magnetized? This tools is for anisotropic magnets only, magnets with a single direction of magnetization.
Scale only affects the drawing. You might need a decimal for large magnets or unit changes. 0.5 or other values less than 1 are valid. :1 Scale change? ×
This pops up a link to get back to this page with the same magnet configuration. Save Magnet (create link)
This re-loads the page back to default everything. It will forget all your inputs. Start a New Magnet (defaults all)







Download PDF Download STEP
Specify material properties. This will override the default from the material selection box on all pages, including the calculated results and curve. Try out different ones to see how the results of the curve change or the force changes!
Material Overrides:
Where the curve crosses the Y-axis. Br is the Average B of a closed-circut or infinitely-long magnet. Essentially the highest potential B of the magnets underlying material without any external field helping push it higher. Tesla (Residual Induction)
Essentially the slope of the linear section in the B-H curve. Permeability (μr or mu-relative) is a measurement of how close flux lines can get as they pass through a material. It can be thought of as the "conductivity" of a magnetic material in a way. It is relative to the permeability of vaccuum (μ0,that has units). Unitless

This value only affects the calculated value in the title of the Flux Density at the pole curve. This airgap is how far your Hall-Effect (Gauss or Tesla reading sensor) is from the center of the pole of the magnet. If you are using a Gaussmeter or Teslameter, the sensor is probably embedded a little ways inside the probe affecting your reading. Assume at least 0.5mm. mm (curve title)
This value only affects the Force curve to steel. This airgap is how far the magnet is from the steel. It doesn't have to be air. Anything non-magnetic could be in this gap, It could be plastic or aluminum. mm (curve title)
Where the intrinsic (taller) curve crosses the X-axis. Hcj (or Hci, intrinsic coercivity) is the magnet material's resistance to demagnetization. You can heat up, or put an external opposing field on a magnet and demagnetize it or flip its magnetziation 180 degrees if the opposing field is high enough (reverse magnetize). Even a magnet's own internal field can demagnetize it if it's Pc is low enough. kA/m (Coercivity)
Essentially where the normal (shorter) curve starts to become non-linear. It's roughly the coercivity where some slight demagnetzation can start to occur. It is measured as the field strength where J (the intrensic flux density average of the magnet) is at 90% of where it started (the J curve should have started at Br). So the X value where Y has decreased 10%. kA/m (where J is 90% of Br)
The temperature coefficent of Br. For every degree C the temperature changes, Br will change this percentage. This is an approximation, this value is not linear outside of a small range, but this is close enough in the working temeprature range of the magnet. %/°C (Tc of Br)
The temperature coefficent of Hcj. For every degree C the temperature changes, Hcj will change this percentage. This is an approximation, this value is not linear outside of a small range, but this is close enough in the working temeprature range of the magnet. %/°C (Tc of Hcj)
Temperatures for which to draw curves, comma sepearted, in degrees C. Due to the temperature coeffients above changing the magnetic properties with temperature, we have a slightly different curve as the temperature changes. It is helpful to check many temperatures with your magnet's Pc to see at which temperature you risk demagnetization. °C
By default the curve draws a line that corresponds to the Permeance Coefficent of the magnet you created (this is shape dependent, so the dimensional settings). If you'd like to test a different Pc without changing the magnet dimensions, you may enter it here and it will show up on the curve. Where your Pc crosses the normal (shorter) curve is the magnet's operating point. If that is before the knee you are not yet demagnetizing the magnet (on average, every spot in the magnet technically has a separate Pc, this is an average for the entire shape). Unitless

Traditional uses simplified formulas for quick magnet calculations. Realistic uses my own touch of number massaging (using a lot of data and statistical non-linear regression as well as some experience) to estimate a more realistic number. This only works in a certain range of Pc's and sizes. Where it's known to grow increasingly inaccurate the calculation will automatically return to traditional. This system changes frequently.
Traditional     Realistic (Experimental)
The type of unit to be converted. There is some overlap (between Flux Density and Field Strength), but mostly the units are different in each. Pick a category to find your unit.
The number to convert FROM. The conversions will appear in the window on the right. It will convert from the given unit to every reasonable unit in the library.
The unit to convert FROM. The conversions will appear in the window on the right. It will convert from the given unit to every reasonable unit in the library.

Not proper means this unit-type shouldn't be converted to this unit. It is equivalent, but not techincially correct. For instance moment is in Am2. You CAN convert to Tm3 or Wbcm, but this is no longer REALLY a moment. It's a flux-distance. This converts some weird things that shouldn't be converted, but you might need to as some Fluxmeters output flux-distance instead of moment when using a Helmholtz or other read coil.

Note for Helmholtz users - If your Fluxmeter is giving you a flux value (which it likely isn't measuring), multiply it by the coil constant (written on the coil likely) in its distance unit to get a flux-distance you can convert to moment.

You may turn off the normal (B) or intrinsic (J) curves for each temperature by clicking them in the legend.

You can also turn off Pc (by clicking in the legend) or draw an example Pc using the manual Pc input in the overrides area. If you want to use the Magnet's calculated Pc again, make the manual input blank or 0.

Changing the material dropdown box will reset all overrides.

Beware the very high temp charts of SmCo. α and β aren't linear over a large range.

Possible risk of partial demagnetization in shipping and open-circuit use! (60C)
Only calculates cylinders magnetized through thickness.
Forces:
The force to an identical magnet. If you stacked two of the same magnet's together, this is the holding force between them on the center axis. This is estimated, please use FEA software and a magnet engineer to determine a realistic force.   N
The force to a piece of steel if the magnet had another very large piece of steel behind it. This is the holding force between them on the center axis. This is estimated, please use FEA software and a magnet engineer to determine a realistic force.   N
The force to a piece of 1010 steel much larger than the magnet. This is the holding force between them on the center axis pulling straight away. This is estimated, please use FEA software and a magnet engineer to determine a realistic force.   N
The force to a piece of 1010 steel much larger than the magnet. This is the holding force between them on the center axis pulling straight away. This is estimated (the whole curve is VERY ESTIMATED! The 0mm airgap is fairly accurate.), please use FEA software and a magnet engineer to determine a realistic force.
Flux Densities:
The flux density measurement at the center of the pole face of the magnet (magnetic orientation direction of the vector only). Most Gaussmeters and Fluxmeters have sensors embedded a distance inside their probes. Assume that distance is at least 0.5mm from the surface. It is impossible to use a sensor to read a 0mm gap (the direct surface of the pole) because every sensor has a read distance.   T (at 0.5mm offset for sensor in probe)
Flux Density from the center of the magnet pole over a distance (magnetic orientation directon of the vector only). If you are using a Gaussmeter or Teslameter, the sensor is probably about 0.5mm inside the probe, so look there. If you are using a hall effect, set the distance from the center of the pole in the "Sensor Airgap" and the value will be in the title of this curve.
Magnetics: If needed, here is an Extensive Unit Convertor.
Sometimes called "load-line" of the magnet. Average B/μH of the magnet. This is dependent on the magnet's shape, thickness in the direction of orientation being most important. The higher the Pc, the more flux coming from the magnet. If the Pc gets too low, the magnet can demagnetize on it's own. Picking a shape is an important part of permanent magnet design because of the Pc.  
Nd = 1/(Pc+1)  
The average flux density of the magnet. This is the flux/unit area average in the whole magnet. In an open-circuit (no other magnets or ferromagnetic materials around) this output is affected by Br of the material and the Pc of the magnet (it's shape). It is lowered by the magnet's internal demagnetization field (H)   T
The average demagnetizing field inside the magnet. A magnet will try to demagnetize itself in an open-circuit based on it's Pc (shape). An infinitely thick magnet will have no internal demagnetization field, therefore B will be Br   kA/m
B x H of the magnet. This is a good indication of how efficent the magnet is at using the potential energy in the given volume. This is the area created under the curve by a rectange with B height and H width. The maximum is usually towards the middle of the curve, So a Pc that is neither too high nor too low. This has little to do with typical magnet design.   kJ/m3
The average flux of the magnet through the center slice of the magnet volume. This is not a useful value in most magnet designs, but can be a possible way to test the magnet.   Wb
The average flux density of the magnet if you ignore the internal demagnetization field. This indicates how much opposing field the magnet can take before small portions of it start to demagnetize. J is mathematically related to B (it's B without the internal H). So if you have one curve, you have them both.   T
The average field at any point inside a magnet. If you were to represent the magnet as a point charge, this is the field it produced. This is directly related to B and J. It is based on the magnet's Br and Pc (shape).   kA/m
Magnetic Dipole Moment is Magnetization (a point measurement) integrated across the entire volume. It shows the magnet's entire "strength". It is often used as a testing property for a magnet (can be measured in a Helmholtz coil with a fluxmeter). It is literally the energy per flux density. You can metophorically think of it as the magnitude of the magnet's reaction in an external field.   Am2
The temperature at which the magnet (in an open-circuit, no other magnets or ferromagnetic materials around) can potentially start to demagnetize. See the interactive demag curve for this temperature. This process starts slow at first, but falls off fast towards total demagnetization.   C (open-circuit)
Physicals:
  mm2
  mm3
  g (density assumed at 7.95 g/cm3)

Example Material Properties

Click a material! It will select that material for your magnet and open the interactive demagnetization curve.

All in SI units. Use the Extensive Unit Convertor if needed.

Tesla kA/m kA/m kJ/m3 %/°C %/°C Unitless °C
Name Composition Br Hcj Hk Max Energy Product Tc of Br (α) Tc of Hcj (β) Permeability Max Temp