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

> 1 µT = 10 mG exactly; S = E²/377 in the far field, so 6 V/m ≈ 95,500 µW/m². Neither applies in the near field.

- Canonical URL: https://emfbase.com/questions/how-do-i-convert-mg-to-microtesla
- Collection: Direct answers
- Record id: `questions:how-do-i-convert-mg-to-microtesla`
- Status: verified
- Last verified: 2026-08-12
- JSON: https://emfbase.com/api/questions/how-do-i-convert-mg-to-microtesla
- Also known as: mG to µT, V/m to µW/m², EMF unit conversion

## Key values

- **Topic:** measurement

## 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](https://emfbase.com/quantities/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.
- [Magnetic flux density](https://emfbase.com/quantities/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.
- [Far field and near field](https://emfbase.com/glossary/far-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.

## Sources

- `nist-si` National Institute of Standards and Technology. *The International System of Units (SI), NIST Special Publication 330*. https://www.nist.gov/pml/special-publication-330 — government, link checked 2026-08-12
- `itu-fs-relations` International Telecommunication Union. *Free-space path loss and power density relations (ITU-R P.525)*. https://www.itu.int/rec/R-REC-P.525/en — standard, link checked 2026-08-12

Data licence: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Dataset version 2026.08.1. Retrieved from EMFBase, https://emfbase.com.

This record is reference data, not medical or legal advice. Regulatory limits, scientific guidelines and precautionary values are labelled separately and answer different questions.