How strong is Earth's magnetic field?

Earth's field is 25-65 μT (0.25-0.65 gauss) depending on location. It's strongest near the poles (~60 μT) and weakest near the equator (~25 μT). This is enough to orient compass needles but very weak compared to permanent magnets.

What's the difference between magnetic flux density (B) and magnetic field strength (H)?

B (tesla) includes the material's response to the applied field. H (A/m) is the applied field alone. In vacuum: B = μ₀H. In materials: B = μ₀μᵣH, where μᵣ is relative permeability. Ferromagnetic materials greatly amplify B relative to H.

How strong are MRI magnets?

Clinical MRI uses 1.5-3 T fields—about 30,000-60,000 times Earth's field. Research MRI goes to 7+ T. These strong fields align hydrogen atoms in your body, allowing detailed imaging. The magnets are superconducting to achieve and maintain such high fields.

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About Magnetic Flux Density Conversion

Magnetic flux density (also called magnetic induction or B-field) measures the strength and direction of a magnetic field at a point. It determines the force on moving charges (Lorentz force: F = qv×B) and current-carrying wires (F = IL×B) in the field. The B-field includes both the applied field and the material's magnetic response, making it the "total" field experienced by charges.

The SI単位 is the tesla (T), equal to one weber per square meter or one kilogram per ampere-second squared. The older CGS unit gauss (G) is still widely used: 1 T = 10,000 G. The tesla is named after Nikola Tesla, the gauss after Carl Friedrich Gauss. Flux density is essential for designing motors, generators, MRI machines, magnetic storage media, and particle accelerators. The Earth's field (~50 μT) to MRI magnets (1.5-7 T) spans about five orders of magnitude.

Our converter handles all standard magnetic flux density units used in physics and engineering.

Common Magnetic Flux Density Conversions

変換元	変換先	乗数
T	G (gauss)	10,000
G	T	0.0001
T	mT	1,000
mT	T	0.001
T	μT	10⁶
μT	T	10⁻⁶
T	Wb/m²	1 (equivalent)
G	mT	0.1
T	kg/(A·s²)	1 (equivalent)

Magnetic Flux Density 単位リファレンス

Tesla (T) – The SI単位 of magnetic flux density, named after inventor Nikola Tesla (1856-1943). 1 T = 1 Wb/m² = 1 V·s/m² = 1 kg/(A·s²). A 1-tesla field exerts 1 newton of force on a 1-ampere current flowing through 1 meter of wire. Reference values: MRI scanner 1.5-7 T, neodymium magnet surface ~1 T, strong electromagnet 2-3 T, superconducting magnets up to 20+ T.

Gauss (G) – The CGS unit of magnetic flux density, named after mathematician Carl Friedrich Gauss (1777-1855). 1 G = 10⁻⁴ T = 1 maxwell/cm². The gauss remains popular because many everyday fields have convenient values: Earth's field 0.25-0.65 G, refrigerator magnet 50-200 G, small DC motor 1000-3000 G. Conversion: divide gauss by 10,000 to get tesla.

Millitesla (mT) – 10⁻³ T = 10 gauss. The practical unit for permanent magnets and industrial magnetic field measurements. Bar magnets typically have surface fields of 10-100 mT. Speaker magnets operate at 100-500 mT in the gap.

Microtesla (μT) – 10⁻⁶ T = 0.01 gauss = 10 milligauss. The standard unit for weak fields: Earth's magnetic field (25-65 μT), household electromagnetic fields (0.01-1 μT), and EMF exposure limits (typically 100-300 μT). Also common for geophysical surveys and archaeological magnetometry.

Nanotesla (nT) – 10⁻⁹ T = 10⁻⁵ gauss. Used in geophysics, space physics, and magnetoencephalography. Earth's field is about 50,000 nT. Variations of 1-100 nT are significant in mineral exploration.

Weber per square meter (Wb/m²) – Exactly equivalent to the tesla by definition. This notation emphasizes the relationship between flux density and total flux: B = Φ/A.