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Oersted to A/m

1 Oersted (Oe) = 63,325,700Ampere per Meter (A/m)

By KAMP Inc. / UnitOwl · Last reviewed:

Result
63,325,700 A/m
1 Oe = 63,325,700 A/m
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How Many A/m in an Oersted?

To convert oersted to ampere per meter, multiply the oersted value by 79.5775. The formula is A/m = Oe × 79.5775. For example, 1 oersted equals approximately 79.58 A/m. This conversion bridges the CGS and SI units for magnetic field strength (also called magnetizing force or magnetic field intensity). The oersted, named after Danish physicist Hans Christian Oersted who discovered the relationship between electric current and magnetism in 1820, is the CGS unit still found in many magnetic material datasheets, especially for permanent magnets and soft magnetic alloys. The ampere per meter is the SI equivalent, used in modern physics and engineering publications. Materials scientists characterizing hysteresis loops, engineers designing electromagnets, and researchers working with magnetic permeability all need this conversion regularly. It is particularly common when B-H curves or coercivity values must be copied from older supplier literature into SI-based reports, software, or standards documents. Because H-field conversions are not powers of ten, they deserve extra care. A quick round-number estimate can help in the lab, but published results should use the full factor.

How to Convert Oersted to Ampere per Meter

  1. Start with the magnetic field strength value in oersted (Oe).
  2. Multiply by 79.5775 to get the equivalent in A/m.
  3. The result is the magnetic field strength in ampere per meter.
  4. Quick estimate: multiply by 80 for an approximation accurate to about 0.5%.
  5. For kilo-oersted (kOe), the result in A/m will be in the tens of thousands — consider expressing in kA/m.

Real-World Examples

Permanent magnet — A neodymium magnet with coercivity of 11 kOe
11,000 × 79.5775 = 875,353 A/m = 875.4 kA/m. This high coercivity means the magnet strongly resists demagnetization.
Soft magnetic material — A silicon steel core with coercivity of 0.5 Oe
0.5 × 79.5775 = 39.8 A/m. Low coercivity in soft magnetic materials means they magnetize and demagnetize easily, ideal for transformer cores.
Earth's field — Approximately 0.5 Oe (horizontal component varies by location)
0.5 × 79.5775 = 39.8 A/m. This is the approximate magnetizing force of Earth's field at the surface.
Magnetic testing — A B-H curve measured up to 100 Oe
100 × 79.5775 = 7,957.75 A/m. Converting the H-axis from oersted to A/m is necessary when publishing hysteresis data in SI units.

Quick Reference

Oersted (Oe)Ampere per Meter (A/m)
163,325,700
2126,651,000
5316,629,000
10633,257,000
251,583,140,000
503,166,290,000
1006,332,570,000
50031,662,900,000
1,00063,325,700,000

History of Oersted and Ampere per Meter

Hans Christian Oersted's 1820 discovery that an electric current deflects a compass needle was one of the most consequential experiments in physics, establishing the fundamental connection between electricity and magnetism. The CGS unit of magnetic field strength was named in his honor. In the CGS system, one oersted is defined as the field strength produced by one gilbert of magnetomotive force per centimeter of magnetic path length. The SI equivalent, ampere per meter, derives from a more fundamental definition: the magnetic field strength produced by a current-carrying conductor is expressed directly in terms of the current (amperes) and the geometry (meters). The conversion factor of 79.5775 (more precisely, 1000/4π) arises from the different treatment of the factor 4π in CGS versus SI electromagnetic equations — CGS uses the "unrationalized" form of Maxwell's equations while SI uses the "rationalized" form. This seemingly arbitrary factor is one of the most confusing aspects of electromagnetic unit conversion and has been a source of errors in scientific literature for decades. The International Union of Pure and Applied Physics has repeatedly emphasized the importance of clearly stating which unit system is being used in magnetic measurements.

Common Mistakes to Avoid

  • Using the wrong conversion factor. The oersted-to-A/m factor is 79.5775 (= 1000/4π), not 10,000 (which converts gauss to tesla). Magnetic field strength and magnetic flux density have different conversion factors.
  • Confusing oersted (H field) with gauss (B field). In CGS units for free space, 1 Oe produces 1 G, but they measure different physical quantities. In materials, B and H differ by the factor of permeability.
  • Forgetting the factor of 4π. The 79.5775 factor includes the rationalization constant (4π) that distinguishes CGS from SI electromagnetism. Omitting this factor leads to errors of about a factor of 12.6.
  • Assuming an H-field conversion tells you the corresponding B-field inside a material. After converting oersted to A/m, you still need the material permeability or magnetization relationship before you can say anything reliable about tesla or gauss.
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Frequently Asked Questions

How many A/m are in one oersted?
One oersted equals approximately 79.5775 A/m. The precise value is 1000/(4π) A/m, which arises from the different rationalization conventions in CGS and SI electromagnetic equations.
What is the difference between H (oersted) and B (gauss)?
H is the magnetic field strength (the "driving" field from currents or permanent magnets), while B is the magnetic flux density (the total field including the material's magnetic response). In free space, B = µ₀H in SI or B = H in CGS. In magnetic materials, B = µ₀(H + M) in SI, where M is the magnetization.
Why is the conversion factor approximately 80 and not a power of 10?
The factor 1000/(4π) ≈ 79.58 reflects the "rationalization" difference between CGS and SI electromagnetism. SI equations include factors of 4π in symmetry-appropriate places (like Coulomb's law), while CGS does not. This distributes the 4π differently and produces non-power-of-10 conversion factors for some magnetic quantities.
Is 1 oersted the same as 1 gauss?
Only in the limited CGS free-space relationship where an H field of 1 Oe corresponds to a B field of 1 G. They are still different physical quantities, and inside magnetic materials the relationship depends on permeability and magnetization, so you should not treat them as interchangeable.
Why do magnet datasheets often use kOe for coercivity?
Coercivity values for permanent magnets are often large, so kilo-oersted keeps the numbers manageable in the CGS convention. The SI equivalent is usually kA/m. Many suppliers publish both because different regions and industries still prefer different unit systems.
Quick Tip

When converting B-H curves (hysteresis loops) from CGS to SI, remember that both axes need different conversion factors: the B-axis converts gauss to tesla (÷10,000), while the H-axis converts oersted to A/m (×79.58). Applying the same factor to both axes is a common error that produces physically incorrect results. Many magnetic materials databases provide properties in both unit systems, so cross-check your conversions against published values when possible.

Sources & References