Magnetic Field Converter
Magnetic flux density (symbol B) describes the strength of a magnetic field at a point. The SI unit is the tesla (T), and the CGS unit is the gauss (G). The exact conversion is 1 T = 10,000 G. This converter handles the full range of practical magnetic field strengths: from nanotesla (geomagnetic measurements) through microtesla (environmental EMF) and millitesla (industrial equipment) to tesla (MRI and superconducting magnets).
Magnetic flux density conversion factors (referenced to tesla)
1 T = 1,000 mT = 1,000,000 uT = 1,000,000,000 nT = 10,000 G = 10,000,000 mG
The exact SI-CGS relation is 1 T = 10,000 G exactly, established by the definition of the magnetic flux quantum and confirmed in NIST SP 811.
Magnetic field strength reference values
- 25 to 65 uT: Earth's surface geomagnetic field.
- 0.3 to 1.0 mT: Near household electrical appliances at 30 cm.
- 1.5 to 3 T: Clinical MRI scanners.
- 7 to 21 T: Research and ultra-high-field MRI systems.
- 45 T: Strongest continuous field achieved (NHMFL, Tallahassee).
Magnetic field converter: frequently asked questions
How many gauss is 1 tesla?
One tesla equals exactly 10,000 gauss. This is the exact SI-to-CGS conversion defined by NIST. Earth's magnetic field is approximately 25 to 65 microtesla (0.25 to 0.65 gauss) at the surface.
What is the difference between magnetic field H and flux density B?
Magnetic flux density B (in tesla or gauss) measures the actual magnetic field strength in a material, including the material's response. Magnetic field intensity H (in A/m or Oersted) measures the externally applied field independent of the material. This converter handles B (tesla and gauss).
What is a microtesla used for?
Microtesla (uT) is commonly used for Earth's geomagnetic field measurements and for workplace electromagnetic field (EMF) exposure assessments. ICNIRP sets occupational exposure limits in microtesla. Smartphone magnetometers measure in microtesla.
What magnetic field does an MRI machine produce?
Clinical MRI machines typically operate at 1.5 T or 3 T. Research machines reach 7 T or more. By comparison, Earth's surface field is roughly 25 to 65 uT, about 50,000 times weaker than a clinical MRI.
What is a nanotesla and where is it used?
The nanotesla (nT) is used in geophysics, magnetometry, and space weather monitoring. One nanotesla = 1e-9 T. The nanotesla was historically called a gamma in geophysics. Geomagnetic variations are often reported in nanotesla.
Official sources
- NIST Special Publication 811: Guide for the Use of the International System of Units (SI).
- BIPM SI Brochure: The International System of Units.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.