Magnetic Field of a Magnet Calculator
SI
Imp
Imperial
Inputs
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Magnet grade
(grade)
Representative remanence values for common permanent-magnet materials. Use the supplier Br value when available.
N35 neodymium (Br ~1.20 T)
N42 neodymium (Br ~1.32 T)
N52 neodymium (Br ~1.45 T)
Ceramic / ferrite 5 (Br ~0.39 T)
SmCo 26 (Br ~1.05 T)
Custom remanence
Custom Br
(B_r)
Custom residual flux density / remanence in tesla from the magnet datasheet.
T
Magnet diameter
(D_m)
Diameter of the circular pole face.
mm
Magnet thickness
(L)
Axial length of the magnet in the magnetization direction.
mm
Distance from pole face
(z)
Distance measured outward from the magnet pole face along the symmetry axis.
mm
Results
Default result
Edit inputs
Axial magnetic field
(B_z)
171.5
mT
Pass
Also computed
Axial field
(B_z)
Pass
0.1715
T
Axial field
(B_z)
1,715
G
Pole-face field
(B_0)
295.2
mT
Field vs pole face
(B_z/B_0)
58.11
%
Remanence used
(B_r)
1.32
T
Thickness / diameter
(L/D)
0.25
Axial field (mT) vs Distance from pole face
The field falls quickly with distance from the pole face. This curve is along the magnet axis only; off-axis fields are not represented.
Axial field (mT) vs Distance from pole face
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entered distance
Distance from pole face (mm)
Axial field (mT)
The field falls quickly with distance from the pole face. This curve is along the magnet axis only; off-axis fields are not represented.
Method notes
3 notes
Uses the closed-form on-axis field for an axially magnetized cylinder: B = Br/2*((L+z)/sqrt(R^2+(L+z)^2) - z/sqrt(R^2+z^2)).
The result is only for the symmetry axis outside one pole face. Off-axis fields, nearby steel, keeper plates, arrays and demagnetization need field solving or measurement.
Grade Br values are representative. Temperature, tolerance, magnetization quality and vendor grade data can shift the real field.
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