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EMF and EMR Conversion Formulas

by / Monday, 18 February 2013 / Published in Healthy Building Inspections & Testing
Minimize EMF exposure

How do you convert microwatts per square meter (uW/m2) into microwatts per square centimeter (uW/cm2)?  How many nanoTesla (nT) are in 2.0 milliGauss (mG)?  We’re asked these questions frequently so we’re providing a few common EMF and EMR conversion formulas and conversion charts for your reference.

EMF and EMR Allowable Limits

“What level of EMF and RF are safe?”  This is a really difficult question that has yet to be fully answered by the scientific community. What we do know, and what is clearly presented in the BioInitiative Report, is that there is cause for concern with current levels of exposure in the US. If our government (FCC, OSHA) followed the precautionary principle we would have much more stringent guidelines for EMF (specifically magnetic fields) and RF (radio frequency) radiation.

The RF limits established by the FCC are actually quite complicated because they allow different power densities for each bandwidth. This makes measuring for compliance with FCC guidelines a rather expensive endeavor.

People get their own EMF meters and don’t immediately understand what the numbers on the screen mean. Now you can translate the numbers from your meter into similar units as used by these existing guidelines. Personally, I lean toward the precautionary principle and like using the Building Biology thresholds whenever possible.

EMF and EMR conversion formulas

Magnetic Field Allowable Levels

How much is too much? That is up to you decide.

EMF and EMR conversion formulas

RF Allowable Levels

Magnetic Field Measurement Conversion Chart

Many people get “EMF meters” that only evaluate magnetic fields. The units on the meter are usually nanoTesla (nT) or milliGauss (mG). Healthy Building Science likes to use milliGauss in our EMF Inspection reports. Fortunately it’s as easy as moving the decimal over 2 places!

EMF and EMR conversion formulas

Magnetic Field Conversion Chart

 

Radio Frequency (RF) Radiation Conversion Chart

The most common RF conversion I run into is for the following: Converting microWatts per square meter to microWatts per square centimeter:

EMF and EMR conversion formulas

RF Conversion Chart

Converting Using EMF and EMR Conversion Formulas

The first two relate to electric fields (kV/m & V/m). After that, the next six are for radio frequency (RF) power levels. And the final four are concerned with magnetic fields. The calculations in the charts all revolve around Watts per square meter (W/m2). So to find the other values if you know W/m2, here are the formulas I used to get them:

V/m = √ W/m2 x 377 (Volts per meter = the square root of the product of Watts per square meter times 377)

kV/m = V/m /1,000 (Kilo-volts per meter = Volts per meter divided by 1,000)

mW/cm2 = W/m2 / 10 (Milli-Watts per square centimeter = Watts per square meter divided by 10)

uW/m2 = W/m2 x 1,000,000 (Micro-Watts per square meter = Watts per square meter times one million)

uW/cm2 = W/m2 / .01 (Micro-Watts per square centimeter = Watts per square meter divided by .01)

nW/cm2 = W/m2 / .000,01 (Nano-Watts per square centimeter = Watts per square meter divided by .000,01

pW/cm2 = W/m2 / .000,000,01 (Pico-Watts per square centimeter = Watts per square meter divided by .000,000,01)

A/m = √ W/m2 / 377 (Amps per meter = the square root of the product of Watts per square meter divided by 377)

mG = W/m2 / 23.9 (Milli-Gauss = Watts per square meter divided by 23.9)

uT = W/m2 / 239 (Micro-Teslas = Watts per square meter divided by 239)

nT = W/m2 / 239,000 (Nano-Teslas = Watts per square meter divided by 239,000)

Some other useful conversion formulas are :

mG = (A/m)2 x 15.774059        A/m = √ mG / 15.774059

nT = mG x 100                         mG = nT / 100

A/m = √ nT / 1,577.4059        nT = (A/m)2 x 1,577.4059

V/m = W/m2 / A/m                 V/m = (mW/cm2 x 10) / A/m

A/m = W/m2 / V/m                 A/m = (mW/cm2 x 10) / V/m

 

And some useful predictive (but possibly inaccurate*) conversions between electric, magnetic, and power units:

V/m = √ nT x 90,103              V/m = √ mG x 9,010.3

nT = (V/m)2 / 90,103              mG = (V/m)2 / 9,010.3

W/m2 = (V/m)2 / 377             mW/cm2 = (V/m)2 / 3,770

W/m2 = (A/m)2 x 377             mW/cm2 = (A/m)2 x 37.7

*Since power flow, electric fields, and magnetic fields are all perpendicular to each other, like the hub, spokes, and rim of a bicycle wheel respectively, these results may not perfectly correlate with measured field readings, depending on the geometry of wiring configurations and measuring distances.

Also, in the conversion tables, you will find some numbers abbreviated with an exponential notation. For instance, 2.41E-07 is really 2.41 times 10 to the negative seventh power, or 0.000000241. And 7.63E+08 is really 7.63 times ten to the eighth power, or 763,000,000.0.

Mind your digits and decimals!

 EMF and EMR conversion formulas and some commentary above provided by Bob Dahse and GeoPathFinder.com, and Rob Metzinger and SLT.co. Thank you both!

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