Magnetic Field Strength Converter
Convert between magnetic field strength units — ampere/meter, ampere turn/meter, kiloampere/meter, and oersted.
Results from this calculator are estimates provided for general informational purposes only, based on formulas, rates, and standards commonly accepted as of 2026. Figures may differ slightly from other calculators or professional sources due to rounding methods, differing assumptions, or regional regulations, and rules may change over time. Always consult a qualified professional — such as a financial advisor, healthcare provider, or other relevant specialist — before making decisions based on these results.
Result
1 A/m = 0.012566371 Oe
1 Ampere/Meter = 0.012566371 Oersteds
1 Oersted = 79.577472 Amperes/Meter
1 A/m in every supported unit
What is a Magnetic Field Strength Converter?
Magnetic field strength, H, measures the magnetizing force applied to a region of space or a material — distinct from magnetic flux density B, which measures how the material actually responds once magnetized. Field strength is what you'd calculate directly from a coil's current and geometry, before knowing anything about the core material sitting inside it. Its SI unit is the ampere per meter, defined as magnetomotive force (ampere-turns) spread over a unit length of the magnetic circuit's path — an ampere-turn/meter is simply the same quantity written out to show that current-times-turns origin. Older CGS-based physics and, notably, the entire magnetic recording industry instead use the oersted, named after Hans Christian Ørsted, who discovered in 1820 that a current-carrying wire deflects a nearby compass needle — the very first evidence that electricity and magnetism were linked.
This converter is used whenever a field-strength figure needs to move between those worlds: translating a coil design's ampere/meter rating into kiloampere/meter for a stronger industrial application, or reading a hard-disk or magnetic-tape datasheet's coercivity rating — conventionally quoted in oersteds — and converting it into modern SI units for a materials calculation. Every unit below is defined relative to the ampere/meter, so any two magnetic field strength units — modern SI or historical CGS — convert directly and consistently.
Conversion chart: Ampere/Meter to Oersteds
Conversion table
| Ampere/Meter (A/m) | Oersted (Oe) |
|---|---|
| 0.01 A/m | 0.00012566371 Oe |
| 0.1 A/m | 0.0012566371 Oe |
| 1 A/m | 0.012566371 Oe |
| 2 A/m | 0.025132741 Oe |
| 3 A/m | 0.037699112 Oe |
| 5 A/m | 0.062831853 Oe |
| 10 A/m | 0.12566371 Oe |
| 20 A/m | 0.25132741 Oe |
| 50 A/m | 0.62831853 Oe |
| 100 A/m | 1.2566371 Oe |
| 1000 A/m | 12.566371 Oe |
Supported Units
| Unit | Symbol | In Ampere/Meter |
|---|---|---|
| Kiloampere/Meter | kA/m | 1000 A/m |
| Ampere/Meter | A/m | 1 A/m |
| Ampere Turn/Meter | At/m | 1 A/m |
| Oersted | Oe | 79.577472 A/m |
About These Parameters
- Value
- The amount of magnetic field strength you want to convert, expressed in the "From" unit. Accepts decimals, and can represent anything from Earth's weak field to the strong fields near industrial electromagnets.
- From Unit
- The unit your input value is currently measured in — a coil design's ampere/meter figure, or a magnetic media datasheet's oersted coercivity rating.
- To Unit
- The unit you want the result converted into. Use the swap button to flip From and To instantly, which is handy when translating a magnetic-media oersted rating into the modern SI ampere/meter or vice versa.
How Magnetic Field Strength Conversion Works
The Formula
Every unit here is defined by a fixed multiplier relative to the ampere/meter. To convert a value from one unit to another:
result = value × (factor of "From" unit ÷ factor of "To" unit)
For Ampere/Meter → Oersted: multiply by 0.012566371. For example, 1 A/m × 0.012566371 = 0.012566371 Oe.
Field Strength H vs. Flux Density B
It's easy to conflate magnetic field strength with magnetic flux density, but they measure different things. Field strength H is the magnetizing force a coil applies, calculated purely from current and geometry — it doesn't care what material, if any, sits inside the coil. Flux density B is how the field actually turns out once a particular material responds to that magnetizing force (see the related Magnetic Flux Density converter). In empty space the two are simply proportional by a universal constant, but inside an iron or ferrite core, B can be thousands of times larger than H alone would suggest, because the material's own magnetism adds to the field.
The Oersted and Magnetic Recording
The oersted, honoring Hans Christian Ørsted's 1820 discovery that current deflects a compass needle, is defined in the CGS-Gaussian system so that one oersted in vacuum produces exactly one gauss of flux density. Despite being a CGS unit, it never really went away in one specific industry: magnetic tape and hard-disk manufacturers still specify their media's coercivity — how strong a field is needed to flip the tiny magnetic domains that store data — in oersteds on virtually every datasheet, decades after SI units took over elsewhere in engineering.
Example
A magnetic field strength of 1 A/m equals 0.012566371 Oe. For scale, Earth's own magnetic field strength is only a fraction of an ampere per meter at the surface, a typical audio cassette tape has a coercivity of a few hundred oersteds, and modern high-density hard-disk media can require well over a thousand oersteds to switch.
Frequently Asked Questions
Is magnetic field strength the same as magnetic flux density?
No — they're related but distinct. Field strength (H, ampere/meter) is the magnetizing force applied by a coil's current and geometry alone. Flux density (B, tesla) is how the field actually turns out once a material responds to that force. In vacuum the two are simply proportional; inside a magnetic material like iron, B can be far larger than H alone would predict.
Why do hard drives and tapes still use oersteds?
Habit and industry-wide standardization: coercivity specs for magnetic recording media have been quoted in oersteds since long before most of the world moved to SI units, and switching an entire industry's datasheets and quality-control processes to ampere/meter would offer little practical benefit, so the convention has simply persisted.
How is ampere/meter related to ampere-turns?
Ampere/meter is magnetomotive force (measured in ampere-turns) divided by the length of the magnetic path it acts over. A coil producing 100 ampere-turns of MMF spread over a 0.5 meter magnetic path produces a field strength of 200 ampere/meter. See the related Magnetomotive Force converter for the ampere-turn side of that relationship.
How strong is Earth's magnetic field in these units?
Earth's surface field strength works out to roughly 0.3 to 0.6 ampere per meter depending on location, or about 0.4 to 0.5 gauss in flux-density terms — far weaker than any industrial magnet, but strong enough for compasses and animal magnetoreception to detect reliably.