Demagnetizing Field Calculator - Free Online Tool

Calculate your demagnetizing field with our free online tool.

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How This Tool Works

The Demagnetizing Field Calculator estimates the internal field that opposes a material's magnetization. Choose a standard geometry, select the magnetization axis, and enter magnetization M in amperes per meter. The tool applies Hd = -N M, where N is the demagnetizing factor for the selected axis.

For a sphere, the factor is one third on every axis. For a thin film normal to z, the z-axis factor is 1 and the in-plane factors are 0. For a long cylinder along z, the z-axis factor is 0 and the x/y factors are one half.

  • Input: Shape, magnetization axis, and magnetization M.
  • Optional input: Aspect ratio c/a for a prolate spheroid.
  • Output: Demagnetizing field Hd in A/m plus Nx, Ny, and Nz.

Why This Matters

Demagnetizing fields are important because the same magnetic material can behave differently depending on its shape and the direction of magnetization. Long, slender parts tend to have a small demagnetizing factor along their length, while thin films have a large factor through their thickness.

Use the result as a quick physics estimate for comparing idealized shapes. Real components may need finite-element modeling or measured material data when edges, holes, anisotropy, or nonuniform magnetization are important.

Common Mistakes to Avoid

  • Do not ignore the axis: the same shape can have different N values on x, y, and z.
  • Keep units consistent: magnetization M and demagnetizing field Hd are both shown in A/m.
  • Use the prolate spheroid input only for c/a greater than 1: values at or below 1 are treated like a sphere by this simplified calculator.

Frequently Asked Questions

Common questions about the Demagnetizing Field Calculator - Free Online Tool

Magnetic field strength is measured in Tesla (SI) or Gauss (CGS). 1 Tesla = 10,000 Gauss. Earth magnetic field is about 50 microtesla.
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Sources & References

International System of Units (SI): magnetic flux and flux density

Magnetic flux and flux density is measured in the weber (Wb) and tesla (T). Conversions between SI and other units use exact, internationally agreed factors maintained by NIST.
→Source: NIST — International System of Units (SI)

International System of Units (SI)

Authoritative definitions for magnetic flux and flux density, from the BIPM SI Brochure (9th edition), the defining reference for the SI.
→Source: BIPM — SI Brochure (9th ed.)

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