How do you convert mG to µT and µW/m² to V/m?

Question

How do I convert between EMF units?

Answer

For magnetic fields the conversion is exact: 1 µT = 10 mG, so 0.4 µT = 4 mG. For radiofrequency in the far field, power density and electric field strength are linked by the impedance of free space: S (W/m²) = E² / 377, and E (V/m) = √(S × 377) — so 6 V/m is about 95,500 µW/m², and 1 V/m is about 2,653 µW/m². Note that this RF relationship holds only in the far field, roughly beyond one wavelength from the source, and never for near-field exposure such as a phone against the head, which is assessed as SAR instead.

Related records

• Power density

  Radiofrequency energy flow per unit area — µW/m² on consumer RF meters, mW/cm² in FCC rules, W/m² in ICNIRP guidelines. 1 mW/cm² = 10 W/m² = 10,000,000 µW/m².

  Quantities & units

• Magnetic flux density

  The quantity an ELF gaussmeter reports, expressed in milligauss or microtesla, used to assess wiring, transformers and power lines. 1 µT = 10 mG.

  Quantities & units

• Far field and near field

  Beyond roughly a wavelength from an antenna the field behaves as a propagating wave and inverse-square estimates apply; closer than that they do not.

  Glossary

Sources

1. nist-si The International System of Units (SI), NIST Special Publication 330 — National Institute of Standards and Technology. government, link checked 2026-08-12.
2. itu-fs-relations Free-space path loss and power density relations (ITU-R P.525) — International Telecommunication Union. standard, link checked 2026-08-12.