Magnetic Field Strength Converter
Instantly convert magnetic field strength with our free converter. See conversion tables, formulas, and step-by-step explanations.
Reviewed by Manoj Kumar, Mathematics Educator
Formula
Converted Value = Input x (From Unit Factor / To Unit Factor)
Magnetic field strength conversion uses the ampere per meter (A/m) as the base SI unit. All other units relate to A/m through fixed conversion factors. The oersted, the CGS unit, equals approximately 79.5775 A/m. Ampere-turn per meter is dimensionally identical to A/m since the turn is dimensionless.
Worked Examples
Example 1: Solenoid Field Strength
Problem:A solenoid has 500 turns, carries 2 A of current, and is 0.25 m long. Find H in A/m and oersted.
Solution:H = N * I / l = 500 * 2 / 0.25 = 4000 A/m\nConvert to Oe: 4000 / 79.5775 = 50.27 Oe\nThis is the field strength inside the solenoid core.
Result:H = 4000 A/m = 50.27 Oe
Example 2: Material Coercivity Conversion
Problem:A permanent magnet has a coercivity of 900 Oe. Express this in A/m and kA/m.
Solution:H = 900 x 79.5775 = 71,619.7 A/m\nConvert to kA/m: 71,619.7 / 1000 = 71.62 kA/m\nThis coercivity indicates a moderately hard magnetic material.
Result:900 Oe = 71,620 A/m = 71.62 kA/m
Frequently Asked Questions
What is magnetic field strength (H)?
Magnetic field strength, denoted H, is the measure of the magnetizing force that creates a magnetic field. The SI unit is ampere per meter (A/m). Unlike magnetic flux density (B), which depends on the medium, H represents the applied magnetizing force independent of the material. In a solenoid, H equals the number of turns times the current divided by the length (H = NI/l). It is sometimes called magnetizing field or magnetic field intensity.
What is the difference between H-field and B-field?
The H-field (magnetic field strength, in A/m) represents the applied magnetizing force, while the B-field (magnetic flux density, in tesla) represents the total magnetic field including the material response. They are related by B = u0 * ur * H, where u0 is the permeability of free space and ur is the relative permeability of the material. In vacuum, B and H differ only by the constant u0, but in magnetic materials, the B-field can be thousands of times larger than what H alone would produce.
What are typical magnetic field strength values?
The Earth magnetic field strength at the surface is about 25-65 A/m (0.3-0.8 Oe). A typical refrigerator magnet produces about 4000 A/m (50 Oe) at its surface. Hard disk drive write heads generate around 200,000 A/m (2500 Oe). Powerful electromagnets in MRI machines operate at field strengths equivalent to millions of A/m. Industrial demagnetizers may apply fields exceeding 80,000 A/m (1000 Oe) to erase residual magnetism.
What is coercivity and how does it relate to magnetic field strength?
Coercivity is the intensity of the applied magnetic field (H) required to reduce the magnetization of a material to zero after it has been magnetized to saturation. It is measured in the same units as magnetic field strength, typically A/m or oersted. Soft magnetic materials like iron have low coercivity values of a few A/m, meaning they are easily demagnetized and are used in transformer cores and electromagnets. Hard magnetic materials like neodymium magnets have coercivity values exceeding 800,000 A/m, making them resistant to demagnetization and suitable for permanent magnets. Coercivity is a critical parameter in selecting materials for magnetic storage, motors, and shielding applications.
References
Reviewed by Manoj Kumar, Mathematics Educator · Editorial policy