Skip to content
ToolBoxGeniehome

Magnetic Field Converter

Converters · Added

Magnetism is measured in two different quantities that are easy to confuse. Flux density is how strong the field is at a point; flux is that density multiplied by an area. Each converts within itself here, because turning one into the other needs an area no converter has.

Which quantity?

Flux density is how strong the field is at a point — teslas, or gauss in the older CGS system. Flux is that density multiplied by an area, in webers or maxwells. One weber is one tesla over one square metre, so converting between the two needs an area this page does not have, and each quantity converts only within itself. For a sense of scale: the Earth's field is about half a gauss, a fridge magnet around 50, and an MRI scanner 1.5 to 3 tesla — which is 15,000 to 30,000 gauss.

Result

1 G in millitesla

0.1 mT

1 G = 0.1 mT

The same value in every unit

Tesla (T)
0.0001
Millitesla (mT)
0.1
Microtesla (µT)
100
Nanotesla (nT)
100,000
Weber per square metre (Wb/m²)
0.0001
Gauss (G)
1
Milligauss (mG)
1,000
Kilogauss (kG)
0.001
Gamma (γ)
100,000

One gauss is exactly 10⁻⁴ tesla by the CGS definition, so the conversion is exact rather than measured. A tesla is a weber per square metre, which is the same unit under a different name.

How to use the magnetic field converter

  1. 1Choose flux density if you have teslas or gauss, and flux if you have webers or maxwells.
  2. 2Enter the value and pick the unit it is in.
  3. 3Pick the unit you want, and read the full table beneath.
  4. 4To cross between the two quantities, multiply or divide by the area yourself.

Examples

A fridge magnet

Input
50 G
Result
5 mT — the CGS units survive because the numbers are convenient at this scale

An MRI scanner

Input
3 T
Result
30,000 G

About the magnetic field converter

Flux density, flux, and why the distinction matters

Flux density describes the field itself: how strongly it acts on a moving charge or a current-carrying wire at a particular point. It is what a gaussmeter measures and what a magnet's specification quotes.

Flux is the total amount of field passing through a surface — density times area, with the angle taken into account. It is the quantity in Faraday's law: a flux changing at one weber per second induces one volt. That is why a weber is also a volt-second, and why transformer and generator design is written in flux rather than flux density.

A sense of scale

The Earth's field is roughly 0.25 to 0.65 gauss depending on latitude, which is 25 to 65 microtesla. A refrigerator magnet is around 50 gauss. A strong neodymium magnet reaches a few thousand gauss at its surface. A clinical MRI scanner runs at 1.5 or 3 tesla — 15,000 to 30,000 gauss — and research magnets go past 20 tesla.

At the other end, the fields that magnetic surveying and biomagnetism deal with are measured in nanotesla and picotesla, which is why the gamma and the nanotesla both persist. The range from a magnetoencephalogram to a research magnet spans about fifteen orders of magnitude.

Frequently asked questions

Is the tesla-to-gauss conversion exact?
Yes. One gauss is defined as exactly 10⁻⁴ tesla, which makes every conversion here a decimal shift rather than a measurement. The same holds for the maxwell: exactly 10⁻⁸ weber. These are definitional relationships between the SI and CGS systems, not experimentally determined ones.
Why can it not convert tesla to weber?
Because they measure different things. A weber is a tesla multiplied by a square metre — flux is flux density integrated over an area — so the conversion needs the area of whatever the field is passing through. That is a property of your setup rather than of the units, so the two quantities are kept in separate families with no path between them.
Why do gauss and milligauss refuse to die?
Because the numbers land where people can use them. The Earth's field is about half a gauss and a fridge magnet around fifty; in tesla those are 0.00005 and 0.005. Magnet suppliers, EMF meters and a good deal of geophysics still label in gauss and milligauss for exactly that reason, even though SI replaced the unit decades ago.
What is a gamma?
A geophysics unit equal to one nanotesla, used for the small variations in the Earth's magnetic field that magnetic surveying measures. It is listed here because survey data and older geophysical literature are still written in it, and the conversion is exact.

Related tools