Magnetic Field Converter
Convert tesla, gauss, oersted, ampere per metre, weber and maxwell — keeping flux density, field strength and total flux apart, which most converters quietly refuse to do.
Magnetic Field Converter
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Relative permeability is treated as a single number, whereas real ferromagnetic materials follow a hysteresis curve whose slope varies with field strength and magnetic history.
- Crossing to or from total flux is refused because it requires an area from your magnetic circuit.
- Field-strength bands are omitted deliberately, since the resulting flux density depends entirely on the material.
In short: Magnetism is not one quantity but three. Flux density B is measured in tesla and gauss (1 T = 10,000 G). Field strength H is measured in ampere per metre and oersted (1 Oe = 79.577 A/m). Total flux Φ is measured in weber and maxwell (1 Wb = 10⁸ Mx). Converting between B and H requires B = μ₀μᵣH, so tables printing ‘1 Oe = 0.0001 T’ are silently assuming a vacuum.
Formula
Conversions run within each quantity by a fixed factor. Crossing between flux density and field strength uses B = μ₀μᵣH and therefore depends on the medium. Crossing to total flux additionally needs an area.
Worked Example
- Identify which quantity you have. Tesla and gauss are flux density; oersted and A/m are field strength; weber and maxwell are total flux.
- Convert within that quantity. 1 T × 1 = 1 T.
- Divide by the target factor. 1 ÷ 0.0001 = 10,000 G.
- To cross B and H, name the medium. B = μ₀μᵣH, so 1 Oe gives 1 G in vacuum but 4,000 G in silicon steel.
- To reach total flux, supply an area. Φ = BA, which this converter deliberately will not guess.
Why ‘1 oersted = 1 gauss’ is a trap. In vacuum, B = μ₀H, and the CGS system was constructed so that the numbers coincide: one oersted of field strength produces exactly one gauss of flux density. Because that is tidy, a great many conversion tables list oersted and gauss as though they were interchangeable units of the same quantity. They are not. Put the same one oersted of magnetising force into silicon steel with a relative permeability around 4,000 and you get 4,000 gauss. The coincidence holds only in air, and every magnetic circuit that matters has iron in it.
Strengths & Limits Of This Model
Where this engine is strong
- Separates flux density, field strength and total flux instead of listing all three in one misleading dropdown.
- Refuses the B to H crossing until a medium is named, rather than silently assuming vacuum.
- Derives the oersted factor as 1000/4π rather than transcribing a rounded 79.58.
Where it stops
- Does not model hysteresis or saturation.
- Will not convert flux to flux density without an area.
- Not a magnetic circuit or motor design tool.
Practical Use Cases
Permanent magnet specification
Remanence is quoted in gauss or tesla and coercivity in oersted or A/m. They are different quantities and a datasheet uses both, which is exactly where the confusion begins.
MRI and medical physics
Scanner strength is quoted in tesla while fringe-field safety contours are often mapped in gauss; the 5 gauss line is the conventional exclusion boundary.
Transformer and motor design
Core flux density in tesla determines saturation, while magnetising force in A/m determines the current needed to reach it. The B-H curve of the material connects them.
Geophysics and magnetometry
Earth’s field is quoted in nanotesla, historically called gamma, and survey anomalies are fractions of that — pair with the Inductance Converter when working through sensor coil design.
Methodology & Editorial Standards
This converter treats magnetism as the three distinct physical quantities it actually is. Magnetic flux density B routes through the tesla, with the gauss at exactly 10⁻⁴ T. Magnetic field strength H routes through the ampere per metre, with the oersted at 1000/4π = 79.57747154594767 A/m. Total magnetic flux Φ routes through the weber, with the maxwell at exactly 10⁻⁸ Wb. Conversions within a quantity use exact factors. Crossing between B and H applies B = μ₀μᵣH with μ₀ taken as exactly 4π × 10⁻⁷ H/m, and the engine refuses the crossing until a relative permeability is supplied, because no fixed factor exists. Crossing to or from total flux is refused outright, since Φ = BA requires an area that belongs to your magnetic circuit rather than to the units. The relative permeability of real ferromagnetic material is itself a function of field strength and history, so any single value is an approximation to a hysteresis curve. All conversion factors are exact by definition under the International System of Units, or exact by international agreement where the unit is defined by treaty. Values are held at full IEEE-754 double precision internally and rounded only for display, so chained conversions do not accumulate drift.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Magnetic Field Converter — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How many gauss are in a tesla?
Exactly 10,000. One gauss is 10⁻⁴ tesla, and both measure magnetic flux density, so this is a genuine unit conversion with no assumptions attached. Earth's field of about 50 microtesla is half a gauss, a fridge magnet is around 50 gauss, and a 1.5 tesla MRI scanner is 15,000 gauss.
Is an oersted the same as a gauss?
No, and this is the most common error in magnetics. The gauss measures flux density B and the oersted measures field strength H, which are different physical quantities. They happen to be numerically equal in vacuum, because B = μ₀H and the CGS system was built to make that come out at one to one. Inside iron with a relative permeability of 4,000, one oersted produces four thousand gauss.
What is the difference between B and H?
H is the magnetising force you apply, set by the current and the geometry of your coil. B is the flux density that results, which depends on what material the field passes through. In air they track each other exactly; in ferromagnetic material B can be thousands of times larger, and beyond saturation it stops rising no matter how much H you add. A gaussmeter reads B.
Why can't I convert weber to tesla?
Because a weber is a total quantity and a tesla is a density. One weber spread over a square metre is one tesla; the same weber squeezed through a square centimetre is ten thousand tesla. The relationship Φ = BA needs the area of the surface concerned, which is a fact about your magnetic circuit rather than about the units, so this converter declines to guess it.
What is a gamma in magnetics?
An older name for the nanotesla, used in geophysics and magnetic surveying. One gamma is 10⁻⁹ tesla, which is also 10⁻⁵ gauss. Survey anomalies are typically a few tens of gamma against Earth's background of about 50,000, so the unit is sized for the job it does.
How strong is an MRI magnet compared to Earth's field?
A 1.5 tesla clinical scanner is about thirty thousand times Earth's field and a 3 tesla scanner about sixty thousand times. The safety boundary around a scanner is conventionally drawn at the 5 gauss line, which is 0.5 millitesla, because that is where the fringe field starts to affect pacemakers and where loose ferromagnetic objects begin to be dangerous.
What is relative permeability?
The factor by which a material multiplies the flux density produced by a given field strength, compared with vacuum. Air is essentially 1, silicon transformer steel is around 4,000, and mumetal shielding alloy can exceed 100,000. It is not a constant: it varies with the applied field and with the material's magnetic history, which is what a hysteresis loop describes.
Why do magnet suppliers still use gauss and oersted?
Convenience and inertia. A neodymium magnet with a remanence of 13,200 gauss reads more naturally than 1.32 tesla, and the energy product is traditionally quoted in MGOe, where 1 MGOe is 7.9577 kJ/m³. The CGS units give whole numbers in the range that permanent magnets actually occupy, so the industry has never had a strong reason to abandon them.