Magnetic Field Strength Converter — A/m & Oersted
Convert magnetic field strength (H-field) between different units including A/m, oersted, kA/m, A/cm, and more. Essential for magnetic materials characterization, electromagnet design, and magnetic recording technology. See also our Magnetomotive Force Converter and Magnetic Flux Converter.
Value:
How to Convert Magnetic Field Strength
- Enter the magnetic field strength value in the input field above.
- Select the unit you are converting from in the "From" dropdown menu.
- Select the unit you want to convert to in the "To" dropdown menu.
- The result will automatically appear in the result field.
- Use the copy button to copy the result to your clipboard.
- Click any conversion in the list below to quickly select those units.
Magnetic Field Strength Formula
Magnetic Field Strength (H-field) Definition:
H = B/μ - M
Where:
H = Magnetic field strength (A/m)
B = Magnetic flux density (T)
μ = Permeability (H/m)
M = Magnetization (A/m)
In free space:
B = μ₀H
Where: μ₀ = 4π×10⁻⁷ H/m
Unit Conversion:
1 A/m = 4π×10⁻³ Oe ≈ 0.012566 Oe
1 Oe = 1000/(4π) A/m ≈ 79.5775 A/m
Common Units:
SI: A/m (Ampere per meter)
CGS: Oe (Oersted)
Unit Relationships:
1 A/m = 0.01 A/cm = 0.001 A/mm
1 kA/m = 1000 A/m ≈ 12.566 Oe
1 kOe ≈ 79,577.5 A/m
Solenoid H-field:
H = NI/L (inside solenoid)
Where: N = turns, I = current, L = length
Ampere's Law:
∮H⋅dl = I_enclosedExample Conversion
Problem: Convert 1000 A/m to oersted and kA/m.
Given: H = 1000 A/m
Solution:
• To Oe: 1000 A/m × (1 Oe / 79.5775 A/m) = 12.566 Oe
• To kA/m: 1000 A/m / 1000 = 1 kA/m
Answer: 1000 A/m = 12.566 Oe = 1 kA/m
Technical Details
Magnetic field strength (H-field) represents the magnetizing force that creates magnetic flux in a material. Unlike magnetic flux density (B-field), the H-field depends only on free currents and is independent of the material's magnetic response. It is the fundamental quantity in Ampere's law and is crucial for characterizing magnetic materials through their B-H curves (hysteresis loops).
The oersted (Oe) remains widely used in magnetic materials science, particularly for specifying coercivity of permanent magnets (e.g., NdFeB magnets have coercivity of 10-30 kOe) and magnetic recording media. In SI units, the same quantities are expressed in kA/m. The relationship B = μ₀(H + M) connects H-field to flux density and magnetization in magnetic materials.
Magnetic Field Strength Reference Table
| Application | Typical H-field | Description |
|---|---|---|
| Earth's magnetic field | ~40 A/m (0.5 Oe) | Natural geomagnetic field |
| Magnetic recording | 100-500 kA/m | Hard drive write heads |
| Soft magnetic cores | 10-1000 A/m | Transformer and inductor cores |
| NdFeB coercivity | 800-2400 kA/m | Rare earth permanent magnets |
| Ferrite coercivity | 100-300 kA/m | Ceramic permanent magnets |
| Solenoid (typical) | 1-100 kA/m | Laboratory electromagnets |
| MRI magnets | 10⁵-10⁶ A/m | Medical imaging systems |
| Magnetic saturation (iron) | ~200 kA/m | Maximum magnetization point |
Frequently Asked Questions
What is magnetic field strength (H-field)?
Magnetic field strength (H) is the magnetizing force produced by electric currents. It is measured in amperes per meter (A/m) in SI or oersted (Oe) in CGS. Unlike B-field (flux density), H-field depends only on free currents and geometry, not on the magnetic material present.
What is the difference between B-field and H-field?
B-field (magnetic flux density, in tesla) includes the material's magnetic response, while H-field (magnetic field strength, in A/m) represents only the applied magnetizing force. They are related by B = μ₀(H + M) where M is magnetization. In vacuum, B = μ₀H.
How do you convert between A/m and oersted?
1 oersted = 79.5775 A/m, or equivalently 1 A/m = 0.012566 Oe. The conversion factor is 1000/(4π). For quick estimation: 1 kA/m is approximately 12.57 Oe, and 1 kOe is approximately 79.58 kA/m.
What is coercivity in magnetic materials?
Coercivity (Hc) is the H-field required to demagnetize a material (reduce B or M to zero). Hard magnets have high coercivity (NdFeB: 800-2400 kA/m), while soft magnets have low coercivity (silicon steel: 4-100 A/m). It determines a magnet's resistance to demagnetization.
Why is the oersted still used in industry?
The oersted remains common in magnetic materials science, permanent magnet specifications, and magnetic recording because much historical data and standards use CGS units. Many material datasheets still specify coercivity in Oe or kOe alongside SI values in kA/m.
Objective of Measurement:
Measurement is the most important aspect of our life. We use measurement in science, engineering, business trading, personal life, education, and more other fields. As technology is growing day by day so we need a highly accurate and easy convenient global measuring system in each and every field. It is essential to use standard measurement in every field that everyone to be sure that they not get cheated.
History of Measurement:
In history for measurement people used the human body as a tool. For measuring length used forearm, hand, foot & finger as a unit. The foot, finger is a subdivided shorter unit of a length. This type of measurement is not accurate cause different in size of the arm & finger for different people & some of the countries still using it. In history, there were lots of measuring systems developed but mostly used imperial, the metric system of measurement. We use these systems for measure distances, volume, weight, speed, area etc. Due to this a major problem everyone is facing while doing trading between the countries. A huge improvement in civilization, It necessary to improve measuring standards. Nowadays International Standard (SI) units are used as a global measurement system.
Magnetic Field Strength Conversion - Unit Converter:
Our magnetic field strength conversion converter convert ampere/meter [A/m], ampere/centimeter [A/cm], ampere/millimeter [A/mm], oersted [Oe], kiloampere/meter [kA/m], milliampere/meter [mA/m], millioersted [mOe], kilooersted [kOe], ampere-turn/meter [At/m], ampere-turn/centimeter [At/cm], gilbert/centimeter [Gi/cm], ampere/inch [A/in] vice versa with metric conversion.
Magnetic field strength conversions & its abbreviations
| Unit | Abbreviation | Unit | Abbreviation |
|---|---|---|---|
| ampere/meter | A/m | ampere/centimeter | A/cm |
| ampere/millimeter | A/mm | oersted | Oe |
| kiloampere/meter | kA/m | milliampere/meter | mA/m |
| millioersted | mOe | kilooersted | kOe |
| ampere-turn/meter | At/m | ampere-turn/centimeter | At/cm |
| gilbert/centimeter | Gi/cm | ampere/inch | A/in |
Complete list of Magnetic field strength conversion units and its conversion.
1 ampere/meter [A/m] = 0.012566 oersted [Oe]
1 oersted [Oe] = 79.5775 ampere/meter [A/m]
1 ampere/meter [A/m] = 0.01 ampere/centimeter [A/cm]
1 ampere/centimeter [A/cm] = 100 ampere/meter [A/m]
1 ampere/meter [A/m] = 0.001 kiloampere/meter [kA/m]
1 kiloampere/meter [kA/m] = 1000 ampere/meter [A/m]
1 ampere/meter [A/m] = 1000 milliampere/meter [mA/m]
1 milliampere/meter [mA/m] = 0.001 ampere/meter [A/m]
1 kilooersted [kOe] = 79577.5 ampere/meter [A/m]
1 ampere/meter [A/m] = 1 ampere-turn/meter [At/m]