Magnet Property Calculator BETA
PULL FORCE · SURFACE FIELD · FLUX DENSITY · UNIT CONVERSION
Configuration
Enter diameter in mm
⚠ Inner diameter must be less than outer diameter for ring magnets.
All calculations are approximations based on established magnetostatics formulas. Results assume a single magnet in free space against an ideal steel surface. Real-world values may differ. Test magnets in your actual configuration.
Results
Estimated Pull Force
—lbs
— N (Newtons)
— kg (force)
Surface Field (B)
—G
— T
Field at Distance
—G
— T
Pole Face Area
—in²
— mm²
Volume
—in³
— mm³
Grade Remanence (Br)
—T
— Gauss
BHmax
—MGOe
How is pull force calculated?
▸
Pull force is calculated using the Maxwell Stress Tensor with the method of images (magnet against steel), combined with exact on-axis magnetic field equations.
Disc/Cylinder on-axis field:
B(x) = (Br/2) × [ (L+x)/√(R²+(L+x)²) − x/√(R²+x²) ]
Block on-axis field (Camacho & Sosa):
B(x) = (Br/π) × [ arctan(LW / 2x√(4x²+L²+W²)) − arctan(LW / 2(x+H)√(4(x+H)²+L²+W²)) ]
Pull force (Maxwell Stress Tensor + image method):
F = 2 × B² × A / μ₀
Where:
Br = Remanence (T) | R = radius | L = thickness | x = distance
A = pole face area | μ₀ = 4π×10⁻⁷ | image factor = 2
For rings, force superposition is used: F = 2×B_outer²×A_outer/μ₀ − B_inner²×A_inner/(2μ₀), correctly accounting for different boundary conditions on the outer face (steel contact) vs inner hole (air). For spheres, the exact pole field B = (2/3)×Br is used with an empirical contact geometry correction factor.
B(x) = (Br/2) × [ (L+x)/√(R²+(L+x)²) − x/√(R²+x²) ]
Block on-axis field (Camacho & Sosa):
B(x) = (Br/π) × [ arctan(LW / 2x√(4x²+L²+W²)) − arctan(LW / 2(x+H)√(4(x+H)²+L²+W²)) ]
Pull force (Maxwell Stress Tensor + image method):
F = 2 × B² × A / μ₀
Where:
Br = Remanence (T) | R = radius | L = thickness | x = distance
A = pole face area | μ₀ = 4π×10⁻⁷ | image factor = 2
Neodymium Grade Reference Table
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| Grade | Br (T) | Br (Gauss) | BHmax (MGOe) | Hcj (kOe) |
|---|---|---|---|---|
| N35 | 1.170 | 11,700 | 35 | ≥12 |
| N38 | 1.220 | 12,200 | 38 | ≥12 |
| N40 | 1.260 | 12,600 | 40 | ≥12 |
| N42 | 1.290 | 12,900 | 42 | ≥13 |
| N45 | 1.325 | 13,250 | 45 | ≥13 |
| N48 | 1.370 | 13,700 | 48 | ≥14 |
| N50 | 1.415 | 14,150 | 50 | ≥14 |
| N52 | 1.455 | 14,550 | 52 | ≥14 |
