Convert magnetic flux density (B) between tesla, millitesla, microtesla and gauss.
Magnetism • 7 units
All 7 units on the Magnetic Flux Density Converter are defined against the Tesla (T), so each result is one conversion factor away from a single reference rather than the end of a chain of roundings.
The conversion this page is most often opened for is ready before you type anything: 1 T = 10,000 G. Change either side and every row in the table recalculates with it.
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Magnetic flux density (the "B-field") measures the strength of a magnetic field. Its SI unit, the tesla (T), honours inventor Nikola Tesla and was adopted in 1960; the older CGS unit, the gauss (G), is named after mathematician Carl Friedrich Gauss. The two are linked by a simple factor: 1 tesla = 10,000 gauss.
These units appear everywhere from medicine to industry. MRI scanners are rated in tesla (1.5 T, 3 T, or 7 T for research); loudspeaker and motor magnets, scientific instruments, and hard-drive write heads are often specified in gauss. Because medical and engineering literature mixes both units — and Earth's own field is a fraction of a gauss (about 0.25–0.65 G, or 25–65 µT) — converting between tesla, gauss and microtesla is a routine task.
Quick reference — 1 Tesla (T) is equal to:
| Millitesla | mT | 1,000 |
| Microtesla | µT | 1,000,000 |
| Gauss | G | 10,000 |
| Milligauss | mG | 10,000,000 |
| Kilogauss | kG | 10 |
| Weber/meter² | Wb/m² | 1 |
7 units of magnetic flux density, each a fixed multiple of the T. The table spans 10,000,000:1, from mG (0.0000001 T) to Wb/m² (1 T). Conversion is one multiplication into the base unit and one division out of it, with no lookup table and no approximation.
value_to = value_from × (factor_from ÷ factor_to)1 T = 1 T1 mT = 0.001 T1 µT = 0.000001 T1 G = 0.0001 T1 mG = 0.0000001 T1 kG = 0.1 T1 Wb/m² = 1 Twhere:
Assumptions: Factors are exact definitions. Full double precision is carried internally and rounding is applied only for display.
Result25 T = 250000 G
Converting between tesla and gauss is a fixed factor of ten thousand, but the reason the conversion is needed so often is that different fields settled on different units and never reconciled. Medical imaging quotes tesla, magnet suppliers and instrument makers quote gauss, and geophysics works in nanotesla, so a single problem can require all three.
What makes flux density the governing quantity in design is saturation. Silicon steel stops responding somewhere around 1.5 to 2 tesla and ferrite far lower, near 0.4, and past that point additional magnetising effort produces almost no additional flux. That ceiling is why transformer cores are sized as they are: the core area has to be large enough to carry the required flux while staying below the material's limit, and there is no way to buy back margin by driving the coil harder.
The same units set the boundaries people are asked to respect around strong magnets. The controlled-access line around an MRI installation is drawn at five gauss — half a millitesla — which is only about ten times the Earth's own field, and it is placed there because that is roughly where implanted devices and loose ferrous objects start to matter. A field that seems negligible on the tesla scale is not necessarily negligible in practice.