Magnetic Flux Density Converter

Flux density B is the magnetic flux passing through a unit area. One tesla is one weber per square metre (1 T = 1 Wb/m² = 1 kg·s⁻²·A⁻¹). The converter works through tesla:

result = value × T-per-unit(from) ÷ T-per-unit(to)

• 1 mT = 10⁻³ T
• 1 G = 10⁻⁴ T exactly (so 1 T = 10,000 G and 1 mT = 10 G)

The gauss comes from the CGS-Gaussian system (1 G = 1 Mx/cm²). It is not an SI unit but is still printed on magnet listings and older instruments.

Reference strengths:

• Earth's magnetic field at the surface: about 25–65 µT (0.25–0.65 G). In Pakistan it is roughly 45–50 µT.
• A fridge magnet: about 5 mT (50 G)
• Surface of an N52 neodymium magnet: commonly 0.5–1.4 T, depending on shape
• Clinical MRI scanners: 1.5 T or 3 T; research systems up to 7 T and beyond
• A sunspot: around 0.3 T

B versus H. Magnetic field intensity H (in A/m, or oersted in CGS) is a different quantity from B. In vacuum or air, B = µ₀ × H, and conveniently 1 Oe in air corresponds to 1 G. Inside iron or other magnetic materials the relationship depends on permeability, so you cannot convert H to B with a simple factor there.

Residual flux (Br) and surface field. Magnet datasheets often list Br — the remanence of the material, e.g. 1.43 T for N52. The field you measure at the magnet's surface with a gaussmeter is usually much lower, because it depends on the magnet's dimensions and where the probe sits. Compare like with like.

Safety. Magnetic fields above about 0.5 mT (5 G) can affect some pacemakers and implanted devices; MRI suites mark a 5-gauss line for this reason. The converter does not assess safety; it only changes units.

Hall-effect sensors. Cheap modules such as the A1302 output a voltage proportional to B — typically 1.3 mV per gauss around a 2.5 V midpoint. A reading 65 mV above midpoint therefore means about 50 G, which converts to 5 mT. Datasheets from different vendors alternate between mV/G and mV/mT, and a factor-of-ten mismatch is the usual reason a project reports implausible field strengths.

Tesla to gauss

Inputs: 1, From T, To G

Enter 1 and choose T → G. The tool divides 1 T by 10⁻⁴ T per gauss.

Result: 10000

One tesla is ten thousand gauss.

Earth’s field in millitesla

Inputs: 0.5, From G, To mT

A compass guide says the Earth’s field is about 0.5 G. Enter 0.5 with G → mT: 0.5 × 10⁻⁴ ÷ 10⁻³.

Result: 0.05

0.05 mT = 50 µT.

A 3 T MRI in mT

Inputs: 3, From T, To mT

Enter 3 and choose T → mT. The tool divides 3 T by 10⁻³ T per millitesla.

Result: 3000

3000 mT, or 30,000 G.

How many gauss is one tesla?

10,000 G. One gauss is 10⁻⁴ T.

How strong is the Earth’s magnetic field?

Roughly 25–65 µT depending on location, i.e. 0.25–0.65 G.

Can I convert microtesla?

The tool lists T, mT and G. Divide µT by 1000 to get mT, or by 100 to get gauss.

Is oersted the same as gauss?

Numerically only in air or vacuum. Oersted measures H; gauss measures B.

Why does my N52 magnet measure much less than 1.4 T?

The 1.4 T figure is the material’s remanence Br. The field at the surface of a real magnet depends on its geometry and is often 0.3–0.6 T.

Is a stronger gauss rating always better for a magnetic tool holder?

Not necessarily. Holding force depends on the magnet’s area, the steel thickness and the air gap as much as on the surface flux density. Compare published pull-force figures in newtons or kilograms-force instead.

What does the 5-gauss line mean?

It marks where an MRI field drops to 0.5 mT, a threshold used to keep people with pacemakers at a safe distance.