What's the difference between H and B fields?

H (A/m) is the applied magnetic field strength—what you create with currents or magnets. B (tesla) is the resulting flux density including the material's response. In materials with high permeability like iron, B can be thousands of times larger than μ₀H would predict.

Why do magnet specs use oersteds?

Oersted is a convenient scale for permanent magnet characterization. Coercivity (resistance to demagnetization) typically ranges from hundreds to thousands of oersteds—nice round numbers. The CGS system is also traditional in magnetism research.

How do I calculate H in a solenoid?

For a long solenoid: H = nI, where n is turns per meter and I is current in amperes. H is in A/m. The resulting B = μ₀μᵣnI depends on what's inside the solenoid (air: μᵣ = 1, iron core: μᵣ ~ 1000-5000).

Magnetic Field Strength Converter

About Magnetic Field Strength Conversion

Magnetic field strength (H-field) measures the magnetizing force that creates magnetic flux in a material. It's distinct from magnetic flux density (B-field)—H represents the applied field from currents and external sources, while B includes the material's magnetic response. This distinction is crucial: the same H-field produces vastly different B-fields in air versus iron due to iron's high permeability. H is the independent variable you control; B is the resulting field including the material's contribution.

The SI unit is amperes per meter (A/m), representing magnetomotive force per unit length. The older CGS unit oersted (Oe) is still widely used for permanent magnet specifications, coercivity ratings, and magnetic recording media. The B-H curve (hysteresis loop) that characterizes magnetic materials plots B versus H. Understanding H is essential for magnetic circuit design, material characterization and selection, electromagnet coil design, and demagnetization analysis.

Our converter handles all standard magnetic field strength units used in electromagnetic engineering.

Common Magnetic Field Strength Conversions

From	To	Multiply By
A/m	Oe (oersted)	0.01257 (4π/1000)
Oe	A/m	79.577 (1000/4π)
A/m	kA/m	0.001
kA/m	A/m	1,000
A/m	Gb/cm	0.01257
A/m	A/cm	0.01
Oe	Gb/cm	1 (equivalent)
A/cm	A/m	100
A/m	A/cm	0.01

Magnetic Field Strength Unit Reference

Ampere per meter (A/m) – The SI unit of magnetic field strength, representing magnetomotive force per unit length or equivalently current per unit length in an ideal solenoid. Inside a long solenoid: H = nI, where n is turns per meter. The relationship to B-field in vacuum is B = μ₀H, where μ₀ = 4π × 10⁻⁷ H/m. In materials, B = μ₀μᵣH with relative permeability μᵣ ranging from ~1 (air) to 100,000+ (specialized alloys).

Oersted (Oe) – The CGS unit of magnetic field strength, named after Hans Christian Ørsted who discovered electromagnetism in 1820. 1 Oe = 1000/(4π) A/m ≈ 79.577 A/m. The oersted remains dominant in permanent magnet specifications: ferrite magnets have coercivity ~2000-4000 Oe; alnico ~600-2000 Oe; rare-earth (NdFeB) ~10,000-25,000 Oe. Magnetic recording media also use oersteds for coercivity.

Kiloampere per meter (kA/m) – 1000 A/m, the practical SI unit for magnetic material data sheets and strong fields. Saturation magnetization of iron is about 1700 kA/m. Coercivity of NdFeB magnets is 800-2000 kA/m. This unit avoids the SI-CGS confusion that plagues the oersted.

Gilbert per centimeter (Gb/cm) – CGS unit exactly equal to the oersted by definition. 1 Gb/cm = 1 Oe ≈ 79.58 A/m. This notation makes the relationship to magnetomotive force (gilberts) explicit.

Ampere per centimeter (A/cm) – 100 A/m, occasionally used as a compromise between A/m and the CGS system. Convenient for some laboratory measurements where centimeter scales are natural.