Magnetic Field Strength Calculator
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What is a Magnetic Field Strength Calculator Converter?
A magnetic field strength converter is a tool that converts between units of magnetic field intensity such as ampere per meter, oersted, and kiloampere per meter. It is used in electromagnetic engineering, transformer design, and magnetic material characterization.
History of Magnetic Field Strength Calculator Measurement
The oersted is named after Hans Christian Ørsted, who discovered that electric currents create magnetic fields in 1820. The ampere per meter is the SI unit of magnetic field strength. The transition from CGS to SI units made oersted-to-A/m conversion a common requirement.
About This Magnetic Field Strength Calculator Converter
This magnetic field strength converter supports 4 units including ampere/meter, ampere turn/meter, kiloampere/meter, and oersted. It handles both SI and CGS magnetic field intensity units used in electromagnetic engineering.
Understanding Magnetic Field Strength (H-field)
Magnetic field strength (H) — also called magnetic field intensity or magnetizing force — is a measure of the driving force that creates magnetic flux in a material. It is distinct from magnetic flux density (B), though they are related by the permeability of the medium: B = µH. The SI unit of H is amperes per meter (A/m), while the CGS unit is the oersted (Oe). The H-field depends only on the current configuration, independent of the medium.
Magnetic field strength conversion is essential in magnetics design (transformer cores, inductors), materials characterization (hysteresis curves), electromagnetic compatibility (EMC testing), and geophysics. Magnetic material datasheets often present B-H curves with H in A/m (SI) or Oe (CGS), requiring conversion for analysis. EMC standards specify field strength limits in A/m or dBµA/m, depending on the regulatory body and frequency range.
How to Convert Between Magnetic Field Strength Units
The primary conversion bridges the SI system (A/m) and CGS system (Oersted):
- Identify whether you are working with H-field (A/m, Oe) or B-field (Tesla, Gauss) — they are different quantities.
- The fundamental conversion: 1 Oe = 79.5775 A/m (or equivalently 1000/(4π) A/m).
- Inverse: 1 A/m = 0.012566 Oe = 4π × 10⁻³ Oe.
- For kiloamperes per meter: 1 kA/m = 1000 A/m = 12.566 Oe.
- Verify: in free space, B(T) = µ₀ × H(A/m) where µ₀ = 4π × 10⁻⁷ T·m/A.
Key Magnetic Field Strength Conversion Formulas
Essential relationships between H-field units:
- 1 Oe (oersted) = 79.5775 A/m
- 1 A/m = 0.012566 Oe
- 1 kA/m = 1000 A/m = 12.566 Oe
- 1 A/m = 0.01 A/cm = 10⁻³ A/mm
- 1 A/cm = 100 A/m = 1.2566 Oe
- 1 kOe = 79,577.5 A/m ≈ 79.6 kA/m
- In free space: H(A/m) = B(T) / µ₀ = B(T) / (4π × 10⁻⁷)
Worked Examples — Magnetic Field Strength Conversions
Example 1: A transformer core datasheet shows saturation at H = 800 A/m. Express in oersteds.
Solution:
Conversion: 1 A/m = 0.012566 Oe.
Multiply: 800 × 0.012566 = 10.05 Oe.
Answer: 800 A/m = 10.05 Oe — typical saturation for grain-oriented silicon steel.
Example 2: A permanent magnet specification gives coercivity as 900 kA/m. Convert to kOe.
Solution:
900 kA/m = 900,000 A/m.
Conversion: 1 A/m = 0.012566 Oe, so 900,000 × 0.012566 = 11,310 Oe = 11.31 kOe.
Answer: 900 kA/m = 11.31 kOe — typical for NdFeB (neodymium) magnets.
Example 3: An EMC test specifies a field of 3 A/m at 80 MHz. Convert to Oe.
Solution:
Conversion: 1 A/m = 0.012566 Oe.
Multiply: 3 × 0.012566 = 0.0377 Oe.
Answer: 3 A/m = 0.038 Oe — a relatively mild immunity test level.
Example 4: A solenoid produces H = 5000 Oe. What is this in A/m and kA/m?
Solution:
Conversion: 1 Oe = 79.5775 A/m.
Multiply: 5000 × 79.5775 = 397,888 A/m = 397.9 kA/m.
Answer: 5000 Oe = 397.9 kA/m — a strong magnetizing field for material characterization.
Magnetic Field Strength Conversion Quick Reference
Common H-field conversions for magnetics and EMC engineering:
| From | To |
|---|---|
| 1 Oe | 79.58 A/m |
| 1 A/m | 0.01257 Oe |
| 1 kOe | 79,578 A/m |
| 1 kA/m | 12.57 Oe |
| 1 A/cm | 100 A/m |
| 1 A/mm | 1000 A/m |
| 1 A/m | 4π × 10⁻³ Oe |
| 1 Oe | 1000/(4π) A/m |
| 1 A/m | 0.01 A/cm |
| 10 Oe | 795.8 A/m |
| 100 Oe | 7958 A/m |
| 10 kOe | 795.8 kA/m |
SI and CGS Magnetic Field Strength Systems
In the SI system, magnetic field strength H is measured in amperes per meter (A/m). This unit directly reflects the physical origin: H is determined by current (amperes) and geometry (per meter of path length). For a solenoid, H = nI, where n is turns per meter and I is current in amperes. The SI system cleanly separates H-field (driving cause) from B-field (resulting flux density), with the constitutive relation B = µ₀µᵣH providing the bridge.
The CGS system uses the oersted (Oe), named after Hans Christian Ørsted. In CGS-Gaussian units, the relationship B = H + 4πM (where M is magnetization) uses the same "gauss" for both B and H in free space, which is confusing. The conversion factor 1 Oe = 1000/(4π) A/m ≈ 79.58 A/m arises from the different dimensional definitions in CGS vs SI. Despite SI being the official standard, the CGS oersted remains widely used in the permanent magnet industry, materials science publications, and US magnetic component datasheets.
Real-World Applications of Magnetic Field Strength Conversion
Permanent Magnet Design
Magnet grades are specified by coercivity in kA/m (SI) or kOe (CGS). NdFeB magnets have intrinsic coercivity of 800-2400 kA/m (10-30 kOe). Converting between these is essential for demagnetization analysis and motor design.
Transformer Core Selection
Core loss curves plot watts/kg vs. B at specific H excitation. Datasheet H-axis may be in A/m or Oe depending on manufacturer. Accurate comparison requires unit-consistent B-H curve analysis.
EMC Compliance Testing
Radiated immunity tests specify H-field in A/m (IEC standards) or occasionally in Oe (older US mil-specs). Converting ensures proper test setup and field generation coil calibration.
Geophysical Surveys
Earth's magnetic field strength is approximately 0.5 Oe = 39.8 A/m (total field intensity varies with location). Geomagnetic surveys report anomalies in nanotesla (B-field) or gamma, requiring H-field conversion for susceptibility calculations.
Magnetic Recording
Write head field strength (kA/m or kOe) must exceed media coercivity to record data. Hard disk media coercivity ranges from 200-600 kA/m (2.5-7.5 kOe), requiring matched head design.
Common Pitfalls in Magnetic Field Strength Conversion
The most critical error is confusing H-field (magnetic field strength, A/m or Oe) with B-field (magnetic flux density, Tesla or Gauss). In free space, 1 Oe corresponds to 1 Gauss (a convenient CGS coincidence), but inside a magnetic material with permeability µᵣ > 1, B ≠ µ₀H numerically. A ferrite with µᵣ = 2000 at H = 1 Oe has B = 2000 Gauss, not 1 Gauss. Another pitfall is the 4π factor that appears in CGS-SI conversions: it arises from different conventions for the constitutive equations (rationalized SI vs unrationalized CGS). Some older texts use "ampere-turns per meter" (AT/m) — this is identical to A/m since "turns" is dimensionless. Finally, be careful with "demagnetizing field" direction: H inside a magnet opposes the magnetization, so coercivity is the H required to reduce B to zero.
Key Takeaways
- 1 Oe = 79.58 A/m (exactly 1000/(4π) A/m) — the key CGS-to-SI H-field conversion.
- H-field (A/m) ≠ B-field (Tesla). They are related by B = µ₀µᵣH but are different physical quantities.
- Permanent magnet coercivity: typical NdFeB = 900 kA/m = 11.3 kOe.
- The oersted remains common in industry despite SI being the official standard — always check units on datasheets.
- In free space: 1 A/m corresponds to B = 4π × 10⁻⁷ T = 1.257 µT.
- For EMC: H-field in dBµA/m is also used; 0 dBµA/m = 1 µA/m = 1.257 × 10⁻⁸ Oe.
Metric Conversion Factor Tables for Magnetic Field Strength Converter
| Units to convert | Multiply By The Number | Convert as Unit |
|---|---|---|
| Ampere/meter (A/m) | 1 | Ampere turn/meter (At/m) |
| Ampere/meter (A/m) | 0.001 | Kiloampere/meter (kA/m) |
| Kiloampere/meter (kA/m) | 1000 | Ampere/meter (A/m) |
| Kiloampere/meter (kA/m) | 12.566370614 | Oersted (Oe) |
| Oersted (Oe) | 79.5774715459 | Ampere/meter (A/m) |
| Oersted (Oe) | 0.0795774715 | Kiloampere/meter (kA/m) |
Magnetic Field Strengthconverters & it's abbreviations
| Unit | Abbreviation | Unit | Abbreviation | Unit | Abbreviation |
|---|---|---|---|---|---|
| ampere/meter | A/m | ampere turn/meter | At/m | kiloampere/meter | kA/m |
| oersted | Oe |
Frequently Asked Questions
How do I convert oersted to ampere per meter?
Multiply the oersted value by 79.5775 to get A/m. For example, 10 Oe × 79.5775 = 795.775 A/m.
What is the difference between oersted and ampere/meter?
Both measure magnetic field strength (H-field). Oersted is the CGS unit and A/m is the SI unit. 1 Oe = 79.5775 A/m. Modern engineering uses A/m, while oersted appears in older literature.
What is magnetic field strength used for?
Magnetic field strength (H-field) describes the magnetizing force in a material. It is used to characterize magnets, design electromagnets, and specify magnetic material properties like coercivity.
Is ampere/meter the same as ampere turn/meter?
Yes, they are numerically identical. Ampere turn/meter explicitly references the coil turns creating the field, while A/m is the general SI unit. Both equal 1 A/m.
What is the difference between B-field and H-field?
H-field (magnetic field strength, in A/m) is the applied magnetizing force. B-field (magnetic flux density, in tesla) is the resulting field including the material's response. They are related by B = µH.
Complete list of Magnetic Field Strength conversion units and its conversion.
- 1 ampere/meter = 1 ampere turn/meter
ampere per meter to ampere turn per meter → - 1 ampere turn/meter = 1 ampere/meter
ampere turn per meter to ampere per meter → - 1 ampere/meter = 0.001 kiloampere/meter
ampere per meter to kiloampere per meter →
- 1 kiloampere/meter = 12.566370614 oersted
kiloampere per meter to oersted → - 1 oersted = 0.0795774715 kiloampere/meter
oersted to kilometer per meter →
- 1 kiloampere/meter = 1000 ampere/meter
kiloampere per meter to ampere per meter → - 1 ampere turn/meter = 0.001 kiloampere/meter
ampere turn per meter to kiloampere per meter → - 1 kiloampere/meter = 1000 ampere turn/meter
kiloampere per meter to ampere turn per meter →